I've made a couple of these without much trouble.  I went to my
friendly neighborhood player piano technician who simply pulled down
from the attic a couple of player units that he had no use for.

I disassembled the mechanism, built a frame out of wood, drilled a few
holes and installed the mechanism.  It only handles standard 88-note
rolls, although my roommate needs some A rolls repaired and I'm sure
I can easily build an adapter.  For the flat table itself, I used a
'self-healing' cutting board purchased at my local office supply store.

I'm not sure I'll necessarily agree that it's necessary to have a
curved table, as another author suggested.  I can understand the idea
behind it, but I've not experienced any problems with the tape puckering
when rewound.  Perhaps it has to do with the quality of the tape used.
I use an archival quality acid free tape that is very thin.  It's also
important that the tape is not stretched when it is put on the paper.
I've not yet seen a problem with it puckering.

John W Miller
www.PianoRollStuff.com