Greetings!
I asked this same question a few days ago, having had major problems finding silicon grease locally. After getting many replies, I ended up going to an auto-parts store (Pep Boys) and asking for dielectric grease... they had Permatex brand grease in a 3 Oz. tube (should last the rest of my life...) for $7 and change. I've lubed all of my lights with it since then (using about 1/50 of the tube!) and they all work perfectly - including my A2's which are notoriously picky about clean contacts, etc. I've been VERY happy with this grease so far.
Too much is made of the "non-conductive" part of grease selection - the threads will have no problem completing the circuit even if you use an insulative grease product. At least that's been my experience so far.
Best wishes,
Bawko