Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:3949007.
I was inspired by tollbringer's remix (https://www.thingiverse.com/thing:3843759) to add some fans to the lids of TeachingTech's rear electronics case to keep everything cool.
My specific use case has the stock Ender 3 driver board in the left (when viewed from the front of the printer) compartment (using https://www.thingiverse.com/thing:3731202), and an Orange Pi Zero in the right one (using https://www.thingiverse.com/thing:3794903). These lids are only modified from TeachingTech's original file, so they should fit other compartment remixes as well.
I am also including the 40 mm fan grille that is visible in the pictures. All mounting holes are designed for M3 screws. Using the included fan grille and 10 mm thick fans, 16 mm long screws are a perfect fit.
Update: I slightly modified the lids to fit the Ender 3 Pro. The Pro has a wider Y axis extrusion, so this moves the fans further away from the extrusion so there is no interference between the Y endstop or stepper motor. The thickened region is also moved so it can fit under the extrusion (I also gave it a little more clearance, updating both the Pro and non-pro versions). I don't have a Pro so can not verify that the new parts will fit. Please let me know if they do!