I did a lot of looking for my MZ-3. RCR2's are frequently recommended but they are not quite the same size as CR2's. They are a millimeter or so longer and wouldn't fit in the battery compartment. Watson rechargeable CR2's are closer in dimension but still a little bit bigger. They might fit in the compartment of the G1 but it depends on how much play there is in the battery contacts. If you are primarily concerned with cost, get a 10 pack of CR2's from Tenergy. Real cheap but still good quality batteries.