This is a fan mount made especially for the Geeetech Aluminum Prusa I3 that has the stamped steel carriage. You will need a 40mm computer fan, and M3-10mm screws. Some modification may be required for a proper fit.
If you wish to modify the bracket via Tinkercad, the link is below.
If you wish, you can view the video here: https://youtu.be/p8LYLDQ89QQ
This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/lr3L3utea6U
Geeetech Aluminum Prusa I3