I have several standard Happ 2-1/4" Trackball units w/ mounting plate and red ball. They are NOS as far as I can tell.
They were stored in a big box with the plates attached, so the top of the plates are a bit scratched, but the bottom of the plate is in way better condition. Just flip the plate over, it is the same texture as the top. I will include the mounting bolts that attach the trackball housing to the plate.
$45 plus shipping.