One useful thing you should know is the way cells are numbered. A CR2025 is 20mm dia and 2.5mm thick and a CR2032 is the same dia and 3.2mm thick.I did, it only has a slot, no battery, about 25mm x 6mm. Hence the question
Isn't that the same as my suggestion in post no. 8, which you dismissed as far too big?I'll answer my own question for the archive.
Its an LR 27A 12v