You've pretty much discovered what there is to know.
Look instead at the Dixie Gun Works catalog and see if you like their 'Confederate Sharps', or one of the other CSA-related weapons - they may be easier on the wallet and parts should be available, as well.
Of course, you can use pretty much every weapon from the era, but the reality of it all is the ammunition resupply, as cartridge weaponry was far more difficult to feed than percussion, unless a Federal Quartermaster column was captured, and even then, the Federals were using percussion more than cartridge.
Dixie has some nice stuff - send 'em a $5 bill for their catalog.
Scouts Out!