I've been digging around on the internet, Webike lists some manufacturers names such as Performance Motorcycle Creative "PMC" (big Kawasaki parts source) M-Tech Chukyo and possibly M-Tech which is re-organized from Mugen which was founded by Mr. Honda's son.
I'm guessing PMC is at least partly the source of Yamiya's parts.
I'd like to follow our parts back a bit further. Any other tips?