Here is a very complete list. Of these I have bought mostly from AIM, Centerfire Systems, Century Arms, Cole distributing, J&G sales, and Southern Ohio guns.
These are mostly distributors of milsurps, and not collector antiques. When you send them a copy of your 03 FFL ask to be put on their mailing list to get flyers with what they have. Also many have email flyers as well.
Also, this link keeps pretty well up to date on what is available, and where. http://www.relic-arms.com/