I tried a search on google and there were not many results -

you basically need something like this:

https://www.amazon.com/Kastar-Battery-Replacement-Fujifilm-Charger/dp/B09RJHT1BG?th=1

And a bit of luck to get a replacement battery that is not too old (extended storage in a warehouse reduces the capacity through chemical aging of the battery).

Your original battery should have some model name/number printed on the outside, this will help finding a suitable replacement. (Something like Fuji NP-45 or NP45-A for the Instax share SP-2)