The question just doesn't quite make sense for Cayman. There's a bunch of hotels along Seven mile beach, and a bunch of ops that cover the area, and within that distance doesn't really matter. It's not that far and they'll pick you up for boat dives. Pick the op based on other factors, like for instance you said you want small. Thing is, not all the ops have an actual shop that you would go to, especially smaller ones. And even if they do, the boats may be leaving from different locations anyway.
If you are thinking you want this info to go shore diving from a nearby shop with a shore diving there, there's not that many. There's Divetech at Turtle Reef and Cobalt Coast to the north of SMB, and Eden Rock, Sunset House, and I think Don Fosters to the south all pretty near each other. (You wouldn't actually shore dive from 7MB.) If you are thinking you will want run to some nearby shop to rent tanks to go shore diving other places, not all ops will rent tanks for that so you'd have to check. There are a few other places to shore dive but there's not a lot and access is limited, basically it's not Bonaire.