Both the Impact
https://www.tcarms.com/firearms/muzzleloaders/impact
and the Triumph
https://www.tcarms.com/firearms/muzzleloaders/triumph
fall within your price range. Both rifles have open sights if required or necessary.
T/C rifles are all capable of shooting black powder or its substitutes, including BH209. There is no requirement to change breech plugs. The T/C rifles have breech plugs which flash channels are cleaned by turning a 1/8" drill bit by HAND.
Very good rifles, with many happy owners.