Mike,
I'm modifying a USB-qwerty-keyboard to use for controling the Stop's.
This keyboard (KYE SYSTEMS CORP KB-19e NB) is very slim and the keys are flat. I cover the keys with printed textile.
This print shows the key profile and the text of the stop.
I made this print in drawing program Autocad. By this way I have a cheap stopcontrole but still ofcourse without feedback.
If you like I can mail a photo or a autocad drawing in dwg, dxf or wmf.
Maybe the keysize is the same as your x-key.
Henk