Summary

A very simple 40mm fan mount for the Raspberry Pi.
You will need standoffs to mount to the RPi itself. I used 18mm high standoffs.

Obviously using 5v fans you can power it off the RPI 5v/Gnd GPIO pins.

I printed it with Esun ABS+, 4 walls, 5 layers top & bottom and 100% infill.
Takes about 25min to print.

It shrinks a little using ABS+ and the fan holes became a little tight to mount the fan but it does fit.

Worked for me.