Palmtronic LC-5 battery

[Jeff_Birt]

Doing a search for "LF 1/2 W" I found the following:

https://batteryguy.com/genreic%20battery...ttery.html

Judging by your photo I think you would want something with a larger diameter than 20mm though. It also seems the 3.2mm thickness of the above battery might be too much for your calculator.

The coin cell sizing is easy to figure out if you did not know already. Frist two numbers are diameter in mm. Second two are thickness in 0.1mm (32 = 3.2mm)