It originally had a ML2016 with a 3 pin T25 stlye with an additional hole to accomodate a smaller T14 pinout. The only modern equivalent part I can find is the Maxell ML2032 T25 which is discontinued apparently? The only place with stock (until it runs out) is farnell, but they don’t ship outside the uk.
link to them https://uk.farnell.com/maxell/ml-2032-t25/cell-lithium-coin-rechargeable/dp/3032000
Failling that, non tabbed Maxell ML2032 are available so I’ve tried searching for a holder, through digikey, mouser, ebay and even google. I cant seem to find a single source for 20mm Coin 3pin T25 holders.
Is soldering wires to a non pin compatible holder and using that as a dongle really the only option?