Pawn shops, auction sites, classified adds (for instance I saw a CVA flintlock for $150.00 today and was tempted), word of mouth, and just let others know what kind of rifle you are looking for. Also check gun shops that sell used rifles. I picked up a Black Mountain Magnum at one for next to nothing.

I have had terrible luck in Pawn shops (the ones around here). They thought the rifles they had were solid gold. I even told the shuck at one.. that his muzzleloader was loaded I thought. The ramrod stuck out the end of the barrel almost four inches.. He just shrugged it off.