Hi @junkernaut ,
Here’s the service manual for the camera. Be patient as it takes a little while to go from processing to download after you have passed the security check and clicked on Go to Download, below the document preview box.
Sect 3. of the manual show the disassembly procedure
Here’s a composite of two images from the manual showing the battery location on the mainboard pcb diagram on the right and the wiring diagram on the left.
(click on image to enlarge for better viewing)
The image on the right shows that the part number is 2409-001166.
Also it appears to be a capacitor and not a battery per se, the value being 70000uF (0.07F)
Search online using the part number only to find suppliers. A lot that I checked say that it is available as a special order, but you may find a supplier that has one in stock.