However, I can't figure out which battery I need. I assume the original batteries are no longer made, but surely there's an equivalent?
Does anyone have any idea which battery I can use?
On the bottom of the forum page there is a box containing similar threads , in it is just the one about the same model of camera you have .
https://www.photrio.com/forum/threads/voigtlander-vito-csr-a-not-so-usual-model.134741/
In it the O.P discribes your camera as "Its main feature is a Cds coupled meter."
So yes , it needs a battery .
As already mentioned it's a 1.35 volt cell intended for it , you can by these for hearing aids , though they have a relatively short life .
Or you can buy an adapter to use the 1.5 volt cells in them . Be aware , if you buy an adapter you'll need the type that reduces the voltage as well using a shotty diode ( sp ?) , not just the physical size .
I have several cameras that use these batteries but I just put in a regular PX625 .
The voltage is too high for the meter to work correctly when the battery is new , and as it get's older the voltage drops .
This should therefor give inconsistant readings , IIRC not just due to an inconsistant voltage , but due to it being the wrong voltage can give incorrect readings depending on the light levels .
However , in the cameras I have used these batteries fitted , all the shots have come out fine .
I only shoot negatives ( colour and B&W) , where the film latitude (or printing) probably has covered up any errors in exposures .
Shooting reversal film (slides) you should probably make sure you have the right battery .