Well seeing as the RB30 was never released in Japan, I'm not surprised there's not a lot of support for them over there...
Local business such as Lewis Engines, Proengines, JPC, Spool, RIPS in NZ etc will be your best bet for RB30 stuff.
The majority of RB stuff is generic, such as oil pumps, I got Spool rods for mine, and as for a crank/block you need to hit up a wrecker or the Quokka (or whatever your equivalent trading type paper is).