Hi,
A Kibler colonial or woodsrunner would likely fit the bill. Chambers Mark Silver Virginia rifle would also work. Any Dickert, Oerter, Albrecht, or early Reading gun would be fine. Get a copy of Shumway's Rifles in Colonial America Vol 1 and 2 to see many rifles that could overlap the Rev War. If Triplett was at Cowpens, it was not as part of Morgan's rifle corps. They were already disbanded. Maybe he was in the Virginia militia at the time.
dave