Batteries for the OM-1 really isn't an issue. There are adapters and new style zinc-air batteries that can also be adapted in with common items. I use a Wein cell, and its been in camera for over a year and still performs well. The battery lasts a good long while due to only operating the meter(provided you turn the meter off when not in use). Solid, rugged, and built for the pro market. My OM-1 is 25 years old, and is just now in need of minor touch-up.

Rick