[Arran]

With regards to the power switch on the Philco 91 control, I've often found that when it comes to power switches they often used the same type on several different controls in different makes and models. So if you can't repair the original by cleaning it out or what not you can often salvage one from another control, or sometimes locate a NOS one, and replace the switch and leave the rest of the original control in place.
Regards
Arran