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?