I really like https://www.prusaprinters.org/prints/54922-prusa-i3-mk3-90deg-air-inlet. Unfortunately it sticks out too much, and collides with my camera.
So I made this.
Printed in Prusament PC Blend using standard settings at 0.10mm. No supports are needed.
You will need two M3 screws that are at least 2mm longer than the ones already holding the fan.
I have only tested it on an Original Prusa i3 MK3S+.
The author remixed this model.