It's extremely likely that the rotary pump bearings are a standard
size and an off-the-shelf item.  Take your old bearings to your local
bearing shop and they will almost certainly be able to provide you
with a suitable replacement.  Alternately, take the internal, external,
and height measurements and go online at McMaster Carr or a specialty
provider and order the same bearing type.

Beware the very inexpensive bearing alternatives; it's well worthwhile
to spend two or three times as much to upgrade to a Japanese or
European-made variant.  Does anyone still make bearings in the US?

Cheers!
Roger Wiegand
Wayland, Massachusetts
http://www.carouselorgan.com/