There are no smaller cases made specifically for SNES out there. We are working on some cases, but they would actually be slightly bigger than the UGC, so that doesn't help you.
As for a company that can make the cases, sure, but its not that simple. To make cases like this is quite expensive upfront. Especially injection molded. Yes I company could do them for you, but they will need to be engineered (very expensive), then a die needs to be made (very expensive) and then to make it worth your while you will need to order them in high quantity. You would be better off trying to find a case that's already made for another product that is closer to the SNES size.