Hi David and Joe:
Here's what you need:
www.mouser.comMouser #: 639-CR12600SE-T
Mfr. #: CR12600SE-T COMP-3-1 SOLDER TABS
Manufacturer: FDK Batteries (Formerly Sanyo)
Desc.: Electronic Battery 3V 1500mAh
Price: $9.65 ea.
For other Nagra T owners,
As soon as you disconnect the battery, the RAM loses all the codes and data loaded at power up and user entered values. Sometimes it could be a good thing as Hani found out to clear out the corrupt data. The machine will load factory defalut parameters and operational code at power up. But if you don't want to lose the set up data, I would suggest you get a battery holder with two AA batteries and temporarily solder in parallel with the Nagra battery before removing the old battery. You would solder in the new battery and desolder the AA batteries and you should be good to go.
Good luck!
Ki