I ran into the guy that I bought the little HP encoders from last year
at the montly flea market, and he still has about 30 of them for $5 ea
if anyone is interested. They are the same size as a panel-mount pot
and produce 256 pulses/rev. They have two quadrature leads, +5, and gnd.
I'll see if I can find them in an HP opto catalog.