I am looking for advice.

I am sterile and I am wondering if anybody out there has ever considered using donor sperm to have a child?

Sterile as in azoospermia (complete lack of sperm in semen), or oligospermia (low sperm count)??
I'm asking because if its oligospermia, there's still a possibility that some may be improved with treatment, depending on the pathology, so you may wish to consider that option first before seeking for sperm donors.

Concerning donor sperm, i'm aware that happens here in Lagos.
At least, back then in school, some IVF centres used to come and request codedly for sperm donors.
So, its available in Nigeria and i'm almost 100% sure people will be using it.....maybe a bit under the radar though.

Meanwhile, have you spoken with a Urologist??