Flint lock or caplock & .36 or .50? price point? There is a decently active classifieds section in the blackpowder & cowboy action section over at thefiringline, but the rest of that forum (esp. legal & political) is a tough room to post in.
edit* After looking around, i think i see your problem; it sells for about $600 new. That is gonna make for an expensive used firearm. Maybe it would help you sell it if you posted bore pics & details of the lock & such.