I just saw this post, so I may be too late, and this may not be what you looking for.
I even went to Japanese site but found pretty much the same info as the English page. Material is called 7N01. I'm not a specialist by any mean, so if you google Aluminum 7N01, you get couple hits, so you may be able to get something close?
82' KZ750-R1 cafe racer style. Clip-on, Rear set, Fork-Brace, Mikuni Flat-slide (forgot the size), Kerker.
84' GPz750 (basket case). everything are in pieces.
89' ZX750-H1 (ZX-7 Ninja). Resurrection project are on going with my KZ750. Everything is stock.