Please help, looking for sperm donor.

Summer

My husband has a 0 sperm count. We conceived our first child with a donor and we were very lucky to have found him and be successful on the first try. No our son is almost 4 and we would love to have another, however we cannot use the same person as before. I have looked at donor apps, but they do make me a bit nervous. Does anyone have any suggestions or advice on finding a sperm donor? Anything is helpful thank you.