American Derringer has some pretty interesting models that would be fitting for SASS competition. If you are looking for a very compact carry gun North American Arms makes small caliber revolvers and autos.
Honestly, given the number of small frame autos and lightweight snubnose revolvers out there chambered in effective calibers, the derringer has really become an outdated design. Still, I wouldn't mind picking one up myself just for the collection .
I have one that used to be my grandfathers. They're obsolete and not suited for a carry gun today. Incredibly bad trigger, heavy, single action, not real sights, only two shots....get a jframe or a keltec if you want a modern pocket gun.