I assume that we're talking about the leather drive wheel that moves up
and down to change the roll speed.  The diameter of this leather drive
wheel on my Wurlitzer 146 is very close to 3-1/4 inches.  This is
nothing more than a good stiff piece of 1/4" or 3/8" thickness leather
cut in a circle and clamped between two plates.

They're easy to make.  A saddle maker, or probably a shoe repair shop
can supply the leather.  If you think you'd rather have a thicker drive
wheel you can use two 1/4-inch pieces of leather.  (I think this would
be a little too thick and would reduce the Tempo range).

Remove the assembly, remove the 8 or 10 screws that are around the
periphery of the drive wheel to free the leather.  You can use the old
leather as a pattern to cut and drill the various holes for the shaft
and screws.  With a compass, draw the outer circle, making it larger
that the worn one you're replacing.  The final diameter (probably about
1/4-inch larger than the old wheel) isn't too critical as the drive
wheel will be adjustable as you change speed.

With a utility knife you can cut/trim the leather to the approximate
outer diameter, leaving a little extra to trim off later.  Reassemble
the entire wheel and use a disk or belt sander to carefully grind the
outer circumference to the desired measurement.  I'd leave an extra
1/8-inch of diameter as it will "wear in" after installation.

It's a pretty easy job and probably won't take more than 20 to 30
minutes.  The biggest job is the disassembly to get the wheel out of
the system and put it back in.  The job is very similar on a Wurlitzer
105, but I seem to remember it took a little longer to pull out the
old wheel and reinstall the new one.

Joe Teagarden, Connecticut