Remix of top case from https://www.thingiverse.com/thing:3635490 for raspberry pi 3 A+ only.

Wont win any design awards but prints well without supports and works great. Just push the fan in the side and it should stay held in by friction. I used a spare half-broken 24v ender3 4010 axial fan and powered it with the 5v gpio just fine. Does allow access through to the gpio pins but wires must feed out through the side opening.

Can be printed as is without supports, outer brim might be a good idea but not necessary, a layer height of 0.2mm or less for the sloped overhang to print well should be fine. I printed it with a 0.6mm nozzle at 0.2 layer height and no supports in PLA. Should only need 5-10% infill and a couple of walls. Print walls in Outer/Inner order if possible.

Print upside down with the fan shroud facing down.
Will need to also print the bottom half from the remixed file.