Your co-sponsor should make a trip to the state where he was born and go to its county records office and request a copy. The birth certificate will be issued on the spot. Or if the sponsor attended college/ school in the same area where you live, he could also request a copy from them.
Where I am from, if you submit a request by mail, it can take up to six weeks. If your sponsor has a U.S. passport, that may be sufficient evidence, because you need to submit a birth certificate to get a U.S. passport.
Hope this helps
Kiska
