So far, I've identified the following systems that
need pad replacements
Apple Lisa
Corvus Concept
Terak
Genrad Futuredata
SOL-20
Not that you are likely to find one, but you can add the ETH Lilith to that list.
As an added bonus this system, in its very first operation after a reset,
waits for an input from the keyboard, and will refuse to do anything in
the absence of such input.
As a special bonus my system not only had bad foam disks,
but also a defect microcontroller in its keyboard.
There is bound to be a small market for such disks...
Jos