Some of the cameras mentioned in this thread were designed to use banned mercury cells for their meters (F, Spotmatic, Leicaflexes).

However, that is no problems at all.
There are various solutions.

1) Just put in a modern alkaline or silver cell, using a rubber O-ring or a wad of aluminium foil to make it fit. Some cameras, like the Spotmatic, use meter circuits which are relatively insensitive to voltage variation, so even an alkaline cell, which changes its voltage over its life, will still give accurate results. Other cameras vary in their reaction to using the "wrong" voltage, but in most cases the result will still be accurate enough for most uses using negative film.
Using a silver cell instead and compensating the meter reading, or re-adjusting the meter (very easy to do on a Photomic), readings can be spot-on.

2) Use a silver cell (LR44) with an adapter containing a diode (CRIS is the best known brand, but many others, including DIY, exist).
No compensation or re-adjustment needed. The adapter isn't super-cheap, but use is very easy (it's what I use).

3) Use a Wein cell. Relatively expensive and short life, but no fiddling involved.

4) Use a hearing aid battery. Basically a cheap Wein cell, but needs rubber O-ring or wad of alu foil to fit. Very cheap when bought in bulk.


Very simple really...

The "battery issue" is only such for nay-saying armchair experts, but is certainly not an important factor for choosing a body in real life.