Where can i find parts for a revelation .22 rifle. model R100B?

Revelation was a brand name used by Western Auto hardware stores for guns sold by them, but made by others. If yours is a single shot .22 bolt action rifle, whose safety goes on when you open the bolt, your rifle is a Mossberg Model 320B (Known as the Boy Scout model) The best source for Mossberg parts is Havlin Sales. Add dot com, and you have their address. Mr. and Mrs. Havlin are very nice people, and run the Mossberg Collectors Association. It would have helped to know what part you are looking for.