Whatever you do
Don't loose the original battery! It seems like there are a zillion and one different kinds of these coin cells. Most sights do not have an indication of what battery is right for them. It can be a real issue if you don't know the number for it's replacement.
I have a local store that sells big cardboard packages of assorted coin cells for a couple of bucks. So far so good. Sure beats 5 bucks ea. at wally world.
Freedom is not free