Anyone purchased parts from these folks.  They seem to have some Riding House parts and other unobtainium parts for sale. Would consider using them but don't want my money going into a black hole!

Site for Reference - http://japan.webike.net/ps/S4R/#!search&p.ref=product-search&p.k=S4R&p.p=13

Maybe I'm mistaken, but I *think* these guys talked about selling Riding House parts.
http://www.desmoperformanceparts.com/#/contact/4572275619

Contact them and see what they say - if they don't have it, they'll know who does

I've purchased some from them.
These  (radiator and oil cooler core guard by AELLA)




And this


So long as they have item(s) in stock, their shipping is really fast.
(they shipped out those AELLA core guards July 13th  Saturday evening (18:00), 15th Monday 14:02 it's already in San Francisco (custom), 17th Wednesday 13:41 Delivered to my door.)

They have some of the similarly obscure japanese super moto stuff, so I've seen where folks have bought a few items from them.

Down side - price tend to be high.
Up side - despite the distance shit from japan gets here shockingly fast. I bought direct, not from Webike, a kit to make spoke wheels tubless from Outex. It arrived in 4 or 5 days - I don't get stuff from Cali that fast.

They were the only place I could find that carried an OEM replacement clutch lever for my Nissin radial master at a decent price. Shipping was pretty fast considering where it came from. Packaged nice, perfect item. Wouldn't hesitate with another purchase with them.

Thanks for confirming another wallet draining moto source.  Some of their stuff is just grand!!, LITERALLY