I decided I really needed to build a Steiner keyboard. He offered a 3 and 4 octave at least from the owner's manual. I found a new "old stock" Pratt-Read keyboard from Stephen at Synthwood! That means I won't have to hack a newer one, and it will be truly vintage. I also ordered a set of mod wheels from Synthwood. I'll use the one wheel for the pitch bend. Don't know yet what the other wheel will be good for. Maybe the portamento.
I also ran down some obscure parts for the ring modulator and the keyboard uses a odd MOSFET OpAmp. But, I found them all and have ordered some and to spare. I think the last hard part to find will be some 0.01% 22k resistors. Precision Resistor should be able to make them for me. I'll have to look into it.