I'm trying to compile a list of classified/auction sites that would have C&R guns. So far I am aware of:
Gunsamerica
gunbroker
armslist
gunlistings
gunauction
proxibid
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.
One question for the OP. Are you looking for a source of antiques, and collectible firearms, or for shooters that you can use your C&R FFL to order direct?