I have one of those Universal players that had the same problem.
Fortunately, I was able to get another gearmotor from Barber-Colman.
Unfortunately, they're now out of business.

I might suggest looking at the Jameco Electronics website,
http://www.jameco.com/  They seem to have lots of possible replacements
there.  Also, they have clickable links for product data sheets.

It wouldn't surprise me if the Barber-Colman motors weren't made to some
kind of industrial standard and there are off-the-shelf replacements for
them.  For the kind of production Universal had -- something like 18,000
units total -- I don't think they could have afforded a custom-designed
motor, even back in the 1970s.

Dave Vincent