Peter,
The batteries for the BE-612 and BE-754 are available however if you already have DASH lines on the display you will have to go to the dealer to have the radio reset. They are the only people that have the reset device and even they can't buy replacement ones if their's breaks. No longer available. If you don't have DASH lines but do wish to change the battery you can do so by applying 3.6 volts by soldering a temperary battery across where the battery is located (this is needed to hold the memory) then unsolder the old battery and replace it with the new one. Then remove the temperary battery and you are done.

www.lajollaaudiorepair.com

Cleeve Morrison
La Jolla Audio Repair