Most of my fellow burlesque ladies have been making their own and they say it's really easy! I'm all for craft night with the gals (and some booze) and making all of the things I need for costuming. I've recently been making my own feather hair pieces and mini hats with glitter and sequins and pasties will be my next venture! I will share the tricks I've learned soon. ;)
I generally buy mine from my troop leader who makes Close to your Heart Pasties. But I know that you can order online from Twirly Girl pasties in Seattle, Adora Belle on myspace in the UK, or just try Ebay or Etsey. I've gotten some pretty good ones there as well and reasonably priced.
I love gothfox designs on etsy.com. Beautfiful, soft yet firm, and the array is dizzying! Very fast shipping... just gorgeous! Google gothfox and it'll pop up as one of the first links I believe.
I make most of my own. And, if you're interested, I'd be happy to write up a sort of tutorial for you 'splainin how I do it.
But, if you don't love crafting like I do and you'd prefer to buy, I recommend Gothfox. You can find her on Myspace at www.myspace.com/gothfoxdesigns. She also has an ebay store you can link to from her Myspace. I've had great experience with her- she makes beautiful pasties and is a doll to do business with.
You should definitely check out Gothfox designs. I won't perform without using her pasties. They are super heavy duty and absolutely drop dead gorgeous.
She can also make custom pasties for your routines, but you will need to give her at least a month's notice. All you will need to do is present your idea to her, and she can create anything you'd like. And she's super sweet to boot. http://www.gothfox.com