This is a mini case for a FakeTec Meshtastic DIY board.
It uses a mini spiral antenna from AliExpress

Screws used are  M2x6

Battery is a 1s 220Mah from an RC Airplane

There is room for a 1s battery protection circuit
You can also drill out the holes for the LED with a 1.8mm drill and insert a small piece of translucent filament (like I did with a piece of yellow translucent TPU in the picture)