Clive Page explained :
I've done it on a Philips, which is held together by regular screws and hex
sockets. But my modification was to unsolder the tagged battery from the PCB
and then use a couple of bits of scrap brass to provide contact plates so it
would take a standard AA rechargeable cell just pushed in place. I found
that tagged cells were *much* more expensive than regular ones, and I find
that I have to change the battery every few years.

I agree, tagged cells are more expensive, but using a more aggressive
plumbers flux, you can solder wires to ordinary cells. You can also
spot weld wires, with a bit of experience.