In particular I'm looking for a flintlock pistol or a pepper-box pistol.Any help would be appreciated.
I personally feel that using a scope on/with a muzzle loader defeats the reason for hunting with a front stuffer: But that is me. If legal in your state the scope improves the sight plain and hitting the target. I have taken deer with a front stuffer with open sights out to 150 yards, a scope will only insure a hit and better placement of the bullet.
I don't know about the pepper boxes, but you can find pretty much any repro black powder item at your local Cabela's or Bass Pro.
I always look in Dixie Gun Works (Union City TN) for stuff like that.. they are online.
Try Brocks Surplus in Decatur, Just around the corner from Ponce and N. Decatur. They have a lot of collectible guns. Last time I was there they had several muzzle loaders. 640 Valley Brook Rd Decatur, Georgia 30033 (404) 294-9500