Someone on Amazon bought a GMB mechanical fuel pump in September 2016. Its cheap (at least before you import it!) and he gave it 5 star rating.
The interesting bit is that he says the internals of this GMB pump match the Kyosan Denki pump internals. In effect he has now created a refurbished Kyosan Denki pump (happy days).
The other 240z OEM pump was the Nikki which had slightly different internals. I might have to buy one of these GMB pumps. If it does indeed refurb the Kyosan Denki then i will report back........unless you have been there, done that