The 16mm and the kit zoom use the same barrel size and filters and the hood from the kit also fits on the 16. And although the 16 is wider than the 18 on the kit, the hood doesn't show in the frame. So, if you have the kit also, you're golden. If not, maybe you can order the hood as an accessory?
As for the Contax G adapter, here's one from Fotodiox. Its the most expensive adapter they seem to make for the Nex, but they have one... There may be others for less money out there - dunno?