Does anyone have a p/n for this? Where I can get one?

 

There's one at Radio Shack that works fine; I believe it's their 2.5 amp one. Anything with a higher rating tahn that should work.

All it does, is protect the switches and things from the flyback when the compressor circuit opens. It doesn't "do" anything as far as making the system work; it will work fine without it, just those other contacts might not last as long.

Install it with the band end connected to the wire that brings in the +12V from the low-side cutoff switch.