while I'm agree they could never got serviceable parts, I guess must be around some ppl/shops who rebuilds diaphragms, because servo control is not the only part of the car what it works with vacuum.

i.e.: 68/69 headlight doors actuators, A/C actuators, Big truck brakes systems, Mercedes 116 door lock actuators ( is my case too LOL ), and lot of etcs...

then add to these, lot of medical tools or devices