There is a Swiss-made alternative for round rubber belting called
"Polycord," made of a green synthetic.  Easily installed and durable,
it is also cheaper than leather of comparable size.  When installed, it
is fused with a small flame, such as that of a cigarette lighter, and
becomes a seamless belt.  This material is available in smaller
diameters from :

    Small Parts, Inc.
    13980 N.W. 58th. Court
    Box 4650
    Miami Lakes, FL  33014-0650
    1-800-220-4242
    www.smallparts.com

(They even like band organs, and carry a few recordings in their
catalog!)

I would suspect that one of the sizes listed in the Small Parts catalog
would be suitable for use on a roll frame, but Polycord is also
available in larger diameters than Small Parts, Inc. carries.  Look
under "power transmission equipment," in the Yellow Pages for a dealer
near you, or I can recommend one in the Detroit area, who, I suppose,
would be willing to UPS orders within the U.S., but ask first to be
sure:

    D. P. Brown of Detroit, Inc.
    38451 Webb Dr.
    Westland, MI  48185
    734-722-8900

Good luck, and best wishes for the new year.

Dave Vincent