I believe usabikemotors has the Grubee GenII- at least they did have quite a few a couple of weeks when I talked to them. I can't offer any feedback on the engine or vendor as I went with a different kit.
USABikeMotors.com, Star-Fire Motors and Parts
I think boygofast on ebay offers a similar design but it is not a Grubee branded engine. Once again, I can't offer personal feedback on the vendor or kit. Search 49cc slant engine on ebay.