Dan
Either a CYMA (I don't know if it's gravity or not, but I know it's more reliable than the WELL version) version or an amazing Tokyo Marui one, which is pretty rare, but is very reliable as a backup weapon (it's a bit small for a primary weapon, like the Skorpion). Aside from that, I think you're out of luck. I've been looking for UZI's that weren't from Marui, but I wasn't able to.