Quantity   Component name
1 × Pitchblende sample You can even buy uranium ore on amazon! A radium watch hand would also work.
1 × Geiger counter I used 2 kinds, a traditional gas tube, and a PIN diode. Tube seemed to be better.
1 × Pi Pico W Or any other sutible MCU that can count the clicks with an interrupt pin, and send out or log the data