Old Cameras sometimes take discontinued batteries.

PX625 cameras – Camerapedia

Many old cameras require batteries that are no longer manufactured. This link has a nice chart of cameras that use a particular type of old mercury cell called the PX625. Such as the Yashica 124G, Leica CL, Konica Autoflex, etc. So if you have one of the cameras on the chart look for adapters like this one to allow you to use new fresh batteries. (I haven’t used this adapter yet and can’t vouce for it. If you’ve used it let me know.)