NB: I am extremely territorial about my cosplay efforts and I am looking to have not only the best that I can, but the most unique that I can. I have put in a lot of time and effort and wish to protect the subsequent outcomes I have achieved by ensuring they remain unique. Thanks for your understanding.

Where did you get your Harley Quinn costume from?
My costume has been custom-made for me by an independent Australian costumer/designer of enormous skill and vision. 
I knew when I set out to do this that my goals were too big for me to be satisfied by anything but the best. I needed to find myself a costumer of talent, commitment and attention to detail who was willing to work with me and my penchant for obsessive detail. 
Luckily, I was able to find such a person!
Though we faced the challenge of living in separate states, she overcome it magnificently, and after listening to me pour out my desires and perusing dozens of Bruce Timm illustrations, she has delivered to me a costume I truly believe ranks in the top five of any Harley Quinn costume I have seen the world over.

Where can I get a great Harley Quinn costume from?
If you are looking for a fantastic, accurate and attractive costume, you can't go past Holly Messinger.
If you have sewing skills of your own, she sells her pattern for about $30.
If you would like to make use of her excellent talent and skills, she will custom-make you the costume for about $350.
I personally think this price is highly reasonable (I paid far more than that for both mine) especially for the quality you get.
NB: Holly Messinger is NOT the woman who made my costume. Holly is US-based and her Harley costume is extremely popular, with her being busiest in the lead-up to October. Contact her for further information.

Where did you get your popgun from?
I knew that the perfect popgun would be the best finishing touch on my classic cosplay. Originally I approached a locally-based props manufacturer, but after they quoted me the simply extraordinary fee of $1500, I realised I had to start again.
I approached special effects schools and put out a few bulletins and the solution came from a very unexpected source - a person I barely knew on facebook recommended me to a fellow in far-flung England who makes replica guns for a hobby.
He custom-made me the gun for an extremely reasonable price, again to my specifications - I sent him a few images of Harley with the gun for reference.
What he produced for me far exceeded my wildest imaginings and is something I treasure dearly - it certainly seems to make everyone's eyes pop when they see it!

Does the gun work?
This is always the next question - no it doesn't! I imagine that would up the cost a fair bit - and make it a confiscatable item at conventions! Maybe one day though?

Where did you get your mask from?
The mask is where I got real-properly hardcore cosplayer DIYer - I made it myself!
I did try - and fail - to find someone who could make me a nice little latex mask. Someone suggested that I do it myself, and after some thought and a bit of research the idea didn't seem as crazy as I initially believed. 
Luckily for me, there is a SFX supplies shop local to me, so I marched in there with an image of what I wanted and asked the lady behind the counter to tell me what I needed and how to make what I wanted.
Using her detailed instructions, scribbled in my near-illegible handwriting on the back of the image, plus some further guidance from other hardcore cosplayers online, three weeks of trial and error followed, the outcome of which has been triumph - both a beautiful mask and a reusable mould I can make future ones with. 

Will you make me a mask?
No. Whilst I am very, very happy to share with you information and tips about making your own mask, I do not have the time or desire to reproduce my custom-mask for anyone else. 

Where did you get your other costumes from?
For pretty much all my other costumes outside of the classic Harley Quinn, I have gone to one lady: Holly Messinger.
I have found she produces excellent work with great attention to detail, understands the superhero world and the geek ethic, is committed to accuracy and delivering what you want and works with enormous dedication and intuition. She also relishes a challenge!
The exception to this is the "Dr Quinzel" outfit which was pieced together from various elements I scoured eBay for. 

How much have you spent on your cosplay?
Without disclosing the exact amount: a lot.
Don't get me wrong: I don't spend what I don't have. I don't even have a credit card! My priorities - rent, bills, food, socialising, physical maintenance and all other miscellania of life - are taken care of first, but I work and save hard to have the extra money to commit to this extravagant hobby. 

What sort of makeup do you use?
As a performer, I have tried various types of white facepaint and white foundation for shows in the past so I knew coming into the cosplay that none of that stuff would be any good. DON'T BOTHER WITH IT. It won't apply evenly, will crack and run and streak and won't get you that perfect whiteness either.
The only thing to use is professional-clown quality greasepaint. I recommend "Mehron" brand. You can blend it on with a sponge or apply with your fingers. Finish with white powder and you'll have a fantastic result.
For the rest, the essentials are white eye-liner, black eye-liner, black liquid eye-liner, black false eyelashes, black mascara and black lipstick. That's about it really!
The only other thing I can recommend with the makeup is: practice!

Who takes your photos?
At cons, whoever has the camera!
But for the staged shoots, they're all taken by a very dear and very talented friend of mine. This is her website here and I would highly recommend her - she has a beautiful artistic eye and a great sense of intuition. Yes, she is local to Sydney, Australia. :)

How did you get to this point?
Absolute commitment and passion. None of this fell into my lap, or was given to me. I researched and pursued and worked hard and saved and invested time and energy and money. I have put in an effort commensurate to the quality I wanted to achieve. That's an individual decision for each cosplayer to decide on and I marvel and applaud the efforts of all cosplayers, because it's always a pursuit of passion and unity within our community is about supporting each other. I wanted the best I could personally achieve and that required no small amount of investment on many levels. 
Has it been worth it? Absolutely. The opportunity to dress up as the character I so adore, even if just a few hours a couple of days a year is wonderful, fun, thrilling and delightful - and one of the biggest parts of that is seeing the looks on the faces of other fans and hearing their feedback. 
Keeping a clear head and some reasoned perspective is important, but it's a hobby I'm happy to be totally gung-ho about.