I made a design after not finding it anywhere else. All I had was a 80mm fan. I can not say it is optimal, but it does work. The big gear on the extruder touch the fan, but it does not affect the gear. The most important thing is that it does not go below the hot end. Happy printing!
EDIT: Since it was my first i did it in something simple as tinkercad. It has a lot of bumps which are left from the multiple layers in tinkercad. I will try to make an improved version when I have the time. Feel free to do so if you don't want to wait.
This thing was made with Tinkercad. Edit it online https://tinkercad.com/things/atXtBABDZZx