Dear Rod,  You can probably find the gears that you need for your
Howard nickelodeon roll frame from either Martin Sprocket & Gear or
Boston Gear:

  http://www.martinsprocket.com/gears.htm 
  http://www.bostongear.com/products/open/index.html 

Both probably have distributors in your area.  Stock gears will be a
great deal less expensive than custom made gears.  The straight gears
on your roll frame are simple spur gears.  In order for gears to mesh
correctly, they must have the same pressure angle and diametral pitch.
The pressure angle of 1920's vintage gears is 14.5 degrees, in all
likelihood.

To find the gears that you need, start by measuring the distance from
shaft center to shaft center, then count the number of teeth in each
gear.  To determine the diametral pitch, you can do the following:

*  Measure the center-to-center shaft distance, which we will call "d".
*  Count the number of teeth in each gear, which we will call "N1" and "N2".
*  We will now determine the "pitch radii" of the gears, r1 and r2,
as follows:
   r1 = d / ( 1 + N2 / N1 )
   r2 = ( N2 / N1 ) * r1

*  The "pitch diameter" of each gear is simply double the pitch
   radius:
   d1 = 2 * r1
   d2 = 2 * r2

*  Finally, the "diametral pitch", P, of the gears is:
   P = N1 / d1 = N2 / d2

For example, if the center-to-center shaft distance is 2 inches, the
pinion (smaller gear) has 16 teeth, and the meshing gear has 64 teeth,
then:

  r1 = 2.000 / ( 1 + 64/16 ) = 0.400 inch
  r2 = (64/16) * 0.400 inch  = 1.600 inch
  d1 = 0.800 inch
  d2 = 3.200 inch
  P = 16/0.800 = 64/3.200 = 20 teeth per inch

I would recommend keeping the original roll frame with your piano; it
looks entirely serviceable, and originality is always appealing.

Good luck!

Best Regards,
Tom Chase
Minneapolis, Minnesota