The others mentioned good roundball/conical shooters. I would recommend the RMC Accusporter flintlock (google RMC Sports and check the online catalog). These guns are a little above your budget but would be worth the extra expense in the long run.

Laminated stocks, L&R lock with waterproof pan and roller frizzen; fiber optic sights, choice of 1/48 or 1/28 twist Green Mountain barrels in 24" or 28" lengths, removeable breech plugs. To me they are by far the best flintlock out there. Saboted 300 grain bullets with mmp short black sabots are very accurate from these rifles. It can't hurt to take a look.