I found the best solution for these cameras that use the old PX625 mercury batteries is to make a quick trip to Costco and go the pharmacy and buy a card with 30 ea. 675 hearing aid batteries. These zinc-air batts are about 1.4v nominally and last a couple of months. The batts on the card don't get activated until you remove the blue foil tab. I believe I paid about $10 for the card. I have been running my old cameras on these batts for 4-5 years now. I think it is the best solution for these old cameras. Yep, you have to change them more often but you don't need an adapter, circuit changes, or recalibration of the light meter circuit.
If you are really frugal, you can remove the batts from the camera after use, re-install the little blue tab and put them away. This stops the chemical reaction and discharge of the battery. Like I said, I have the original card from 4-5 years ago and still have a few left. I think the card has a 5-6 year 'use by' date on it.
If your camera is a current hog, take a couple of extras with you when you shoot.
You simply can't beat this solution!