I wrap a 675 hearing aid battery in a metal split washer of the right size. It works great. Much, much better than Wein cells, which IME are terribly inconsistent, short-lived, and expensive. My meters never matched between camera bodies or my hand held light meter when using Wein cells. They always do with the 675's. I have two F-1's and two FT-bs, and they have never matched so well since the discontinuation of the proper batteries. You can get large multi packs of the 675's for very little money.

FWIW, I didn't make up this technique or read it on the Internet. The way I learned of it was from my camera repair person, when I asked him to modify my cameras to take 1.5V alkalines. He said there was no modification necessary. The only drawback is shorter battery life (about 6 months).

However, I feel that the battery issues with the PX625's are a blessing in disguise. The batteries are not needed at all for the mechanical bits of the camera to work properly; they are only needed for the light meter. Not having an in-camera meter will force you to think about lighting constantly, and to rely on experience and/or external meters, which will give you better results by far than any in-camera meter ever made, IMHO. I keep the batteries in as a backup, though I really have not used the camera meters all that often. I check them on a grey card against my spot meter every now and then to make sure they are still fine, so I can rely on them if I need to. They always are, until they aren't, then I replace them for cents, rather than dollars like with Wein cells.

I'd suggest investing in a good incident meter instead of worrying a lot about the ones in your cameras.

It is interesting that the 675 batteries are also zinc-air, or whatever it is called. I had nothing but [expensive] trouble with Wein cells, and no trouble whatsoever with the 675's.