Your best bet is to do what I did and find an old Gossen Luna-Pro/ Luna-Six that is being sold dirt cheap because it needs mercury batteries. There are expensive adapters availible to regulate regular alkaline cells to the required 1.35v, but finding one that will fit *your* camera is a hit or miss affair at best. Wien makes a zinc/air cell, but as Al stated, the lifetime is rediculously short.

The mercury cell your Autocord's meter requires to function properly is no longer available and suitable replacements are usually very expensive. It seems that Al thought you meant battery cell, but he does raise another issue will have to deal with. Fixing the internal meter might be cool for nostalgia reasons, but a used Gossen will be far more useful than the meter on your 'cord. I went through the same thing you are right now, but was convinced by someone I trust to just get a handheld. You could get lucky and find that the problem is only a shorted wire somewhere, but the CdS cell has aged enough by now to require replacing if you want proper readings anyway. The reason people will recommend a handheld meter is because more often than not, the repair cost to your Autocord will be in the range of a new/used meter that will be more accurate anyway. As for the Selenium cell meters, they were never that accurate to begin with and are just about useless 50 years later if you're critical about your exposure (think slide film). I did my homework and asked around and found that most cameras of that era have non functioning meters because either the CdS cell went bad or the electronics went belly up. They were either totally dead, acted the way you describe or were quite inacurate. Out of 7 cameras, not one of them had a properly functioning meter. When I was looking to break into MF photography, I was dead set on getting a camera with an internal meter and had my eye on a couple Autocords, Yashicamats and Rolleicord/flexs with that feature.

Minolta autocord cds iii