I2C breakout and power supply
I2C and Power Supply
This design can also be found on Thingiverse.
The case has cutouts for the USB and Ethernet sockets of the Raspberry Pi2 and Pi3. It will thus only fit on top of the Raspberry Pi2 and Pi3 but not on top of the Pi4.
Additionally four countersunk M2.5 screws of 12mm length are needed.