Use an alternator on the vacuum pump drive. They are very small/light, no drive belt (+ no need for belt pulley on ring gear support), and the weight...
So, he didn't troubleshoot the relay. This is called 'shotgunning' or, as I like to refer to it, 'guessing'. I.e., replacing parts until the problem...
(d) Each person performing an annual or 100-hour inspection shall inspect (where applicable) components of the engine and nacelle group as follows: ...
Check to see if you have a larger panel, somewhere inboard of the power supply. You might be able to remove the hardware and pull the power supply to...