4pcs Mini Thermometer -50~110 Degree Temperature Test Tool Fridge Freezer Aquarium Temperature Meter With Lr44 Battery - Thermometer Hygrometer - AliExpress
8 Best LR44 Batteries 2020 - YouTube
Duracell LR44 Alkaline Button Battery (76A) - Pack of 2 – SNAP UP DIRECT
Test a button cell using a red LED if you have no meter. - YouTube