GUEST - It is unlikely you would find an original bridge without it already being with another banjo. Best bet is probably to take the bridge to a decent music shop (one that sells banjos) and compare it with any bridges they may sell. If you tell us what part of which country you live, people may suggest suitable shops.
If you have to cut slots for strings on a blank bridge, mark the locations with a pencil, start the cuts with a sharp knife, then use a small, fine, triangular file to finish the slots.
GtD.
p.s. GUEST - Mudcat requests guests use a name of some sort so we all know we are talking to the same person.
Quack!