My rpi was thermal throttling so I made this to get some airflow. I decided to go with dual 40mm fans simply for the aesthetics. It uses M3 screws for the fans as well as to mount to the back panel. I've included a template to mark the holes that need drilled/cut.
If you want to have the fans centered you can use this spool holder: https://www.prusaprinters.org/prints/151511-voron-v01-offset-spool-holder
The author hasn't provided the model origin yet.