This is probably better asked on the Domain Names forum.
However, we are not supposed to mention specifics here.
But, what the hey, I suppose I can't get in TOO much trouble simply by mentioning the biggest player that offers what you are asking for - TuCows.
I have no experience with them as a reseller. I just know that they are almost certainly the largest registrar that deals primarily through resellers (it is near 100% of their business) and they have an API for their resellers to use. Dunno if they offer SSL certificates.