I bought my belly cloth from the Player Piano Company.  They also sell
the snaps and the tool to install them.  I don't know what the cloth
is, but it's like a black patent leather on the outside and white
cotton on the inside.  It's nice stuff.

The snaps were identical to those used originally on the piano, so I
didn't have to replace the "female" side of the snaps, which I just
left on the piano.

Ray Fairfield
Morgan Hill, CA