I think it’s the same battery at the BC9500. I use these which fit perfectly as they have the correct pin spacing: https://uk.farnell.com/renata/cr2450-nfh-lf/cell-lithium-button-2pin-3v/dp/1319731
As you can see both pins solder on the same side (other side from the physical battery).
EDIT: After replacing the battery you may need to adjust the FM/AM offset in Test Mode as explained on page 7-3 of the service manual. (That’s assuming you have FM/AM stations in your area with known frequencies)
Location: Warwickshire, UK
My B&O Icons:
