If I go to Radio Shack, I'll get suggestions for substitutes. In my digital caliper, the battery door will fall out. If I use them in a thermometer, the battery tab dosen't quite work, so I had to give up on them.
If you knew what the battery drain was, you might be able to replace with a charge pump, but it might be tough. I also don't know if you can create a "blank battery" with contacts and put the battery(s) external?
By batteries, I mean somthing else and possibly a DC/DC converter. 3 rechargeable AAA's might work directly. A 12 V, "A23" cell with a DC-DC converter might also be a choice, but I think these are not rechargeable. How about something like a 3 cell Ni-CAD portable phone battery pack?