I've got a spare used but working Betson 3" trackball I'd like to trade for a used-but-working Atari trackball, Wico Trackball, or Ultimarc trackball, so I can test with Randy's new Optical board. I'll throw in a USB mousehack to make it worth your while.
I'd also be interested in any other optical controls you may want to offer up. I"ve got other parts I can add to the pot if it's something valuable.
PM me if you've got something.