Ladder chain and sprockets are still made and sold by Stock Drive
Products.  Go to http://www.sdp-si.com/index.asp  Click on
'Product finder' > 'chains' and 'sprockets' to find a large variety
of ladder chains and sprockets.

Typical of many 19th century industrial products, seemingly irrational
'numbered sizes', rather than dimensioned series, were used to
designate the various chain pitches.

Pitches of 65, 48, 42, 34 and 32 links per foot are available.  The
standard size No. 18 (42 pitch x 0.125" wide tooth gap) was used on
Aeolian products.

I bought some new sprockets and chain of that size for my Orchestrelle.
They worked perfectly, although you might have to redrill the shaft
bore (0.188" and 0.250" are standard) to fit your new motor shaft.

Another approach for the high-speed link between the motor and the
transmission input shaft is to use one or more sets of 1/8" neoprene
O-ring belts and precision 1/8-inch grooved sheaves.  This arrangement
has the advantage of being perfectly silent, and allowing a much higher
speed reduction.  Then a pancake motor could be used directly, without
a noisy gear head.

25 years ago, I installed such a system on my Ampico, with a
solid-state variable speed motor.  Seems flimsy, but there is more than
enough torque, and the O-rings lasted over 20 years before breaking.

Stock Drive Products offers a small range of these components, but
W. M. Berg  http://www.wmberg.com/index.htm  offers a much larger range
of sizes (cheaper also), as well as oil-less bronze bearings and
precision ground shaft stock, that you would need to make a perfectly
silent and high-ratio speed reducer.

Richard Vance

 [ Thanks, Richard, and all who responded.  The pancake motor is
 [ PMI (Kollmorgen) type 9FB, 4.75 inch max. diameter.  It will
 [ mount directly below the drive shaft of the Aeolian spool box;
 [ I hope that the antique ladder chain drive will accommodate the
 [ misalignment when the drive shaft and sprocket slide to shift
 [ from play to rewind.  -- Robbie