Flash pads can be purchased through any magic retailer.
I use flash paper a good bit for various effects and ideas in my sleeving routines. Until recently I had used PyroWizard flash pads (as sold through E, for example). But I just got some "inferno paper" (no clue who makes it) and its great. A ton of paper in the pads.
Rocco Silano and david stone have some of the best flash paper routines I have ever seen. David Stone has a routine where a fish is produced from fire... yea...
If you are interested in flash applications check out, "In A Flash" by Jay Sankey, "The Basics Of Sleeving Volumes 1 & 2" by Rocco Silano, "If It Fits, Sleeve It!" By Rocco Silano (book is out of print, but there is a GREAT flash technique for all of you cigarette guys), and "The Real Secrets Of Magic Volumes 1 & 2" by David Stone. All of these have effects and, better yet, techniques for using flash paper.
Hope that helped and don't get burned!!!
Sharp