Re: J-custom MRG-4 and MRG-5...beautiful must see!
The production #'s vary from year to year. The MRG, YCRG and HRG designations are not actually all J-Custom models. They're just models associated with a particular shop for models that were 'customized'. Mind you, I've never seen a MRG and YCRG that wasn't modeled after the J-Custom line, but there are *many* HRG's that were customized J-Custom and prestige models.
YCRG's I've seen very few actually as I think Yamano Music would much rather pump out American Made Fenders/Gibsons. According to a dude that I know at Kurosawa gakki, the MRG-4 and MRG-5's were low in number (think <10 total) this year. Last years MRG production I believe was a total of 18 guitars, 6 black w/cosmo hardware, 6 black with gold hardware and 6 cherry sunbursts with gold hardware. (Gurj you got one of them). HRG models tend to be made in quantities of 2-4 of a particular model.
(There's also IRG models but I don't know which shop that's associated with.. Ishibashi maybe??)
As for getting a hold of new ones? It's a matter of somehow getting one of these Japanese shops to export one to you (or just keep checking the Ishibashi U_Box or that auction site).