I just recently installed a McPherson Upflush toilet that was given to me. The Valve was broken, and not working properly. I did check out web sites only to find that parts where not available. So I did like any good plumber would do.
I figured out how the system worked and created my own.
I placed a board on the wall, and intalled a ball valve, direct water feed to two hose bib fittings.
I also install a back flow preventer into the 1/2" feed.
Now when I want to flush the toilet I turn on the ball valve and shut it off when it is done flushing. (Works like a charm. Better than Valve that came with toilet.)