Gary,  This is from memory, but I believe that piano has a metal
finger behind the take up spool that is lifted by the roll paper.
Once lifted, it releases a normally closed micro switch, which then
supplies the power to the vacuum motor.  These are also called
"Cherry switches".  You _should_ be able to find one at Radio Shack;
if not there, then at Graingers, or McMaster-Carr, or any on-line
electronics supply place.

David Dewey