Ive always heard that invetro ferilization is very effective!! And im sure there are fertility drugs he can take that would help! Good luck and God Bless!
When you say he does not produce sperm, do you mean there are no sperm in his testes or that the sperm sample shows no sperm? If he is not ejaculating any sperm, but still has little swimmers in the testes, I believe you can extract them. Not sure how costly or invasive that is, though...
Good luck to the two of you!