Dixie gun wrks sells a Colt riflr. Not sure what it would take to convert one.
One of my great sorrows was a 12 ga Roper complete with 31 reloadable steel cases and a pair of loading tools for $300.00. Fully enclosed cylinder, not the "cloverleaf" type. 85-90% gun. I bought a Merwn Hulbert Army instead and had $100.00 left over.
Saw a Volcanic carbine the same day for $650 if I remember right.
'Bout 1976, that was.