I purchased my battery mod kit from Wolverine, give them a call and they will hook you up
Installing the kit is quite easy, and initially it solved most of my problems ( except for battery life )
Just last week though, my EOTech went down again and wouldn't power up despite trying several sets of AA batteries
I cleaned the crap out of the contacts at the rear of the battery compartment ( end closest to the optics window ) with rubbing alcohol and an eraser to get it operating again
Quite a few guys at my range are running Aimpoint Micros and are very happy with them
I'm trying to weigh the pros and cons of the Micro for light weight, and the M4S which uses AA batteries