The free-reed piano bellows melodian/Harmonium would be most approapriate for your Civil War reenactments- more proper than a concertina, for they were common to the period. Check out the Hutchinson Family who traveled with one. If you dont like that then maybe you should condider using a period accordian (also more approapriate than concertina); the kind with levered valve openings. I don't play one but I suspect that the set-up may be just the same as the button-type. And you may be able to find a copy of Elias Howe's instruction manual c.1850.