Here's an update to this old design, and an apology for mixing things up so that it wasn't entirely right for a PI4.  I'm sincerely unsure what was going on that made me mix it up like that.

Anyway, here's a new version that is definitely for the RPI4.  It works fine.  I am including the F360 files because I do not plan to go back and make more changes, but you can!

Also, it is designed for M2.5 socket head screws.  The fan needs 8mm screws (the picture shows it with 10mm screws because I am out of the 8's) and the body is designed to use 20mm screws.  They should be just long enough to not stick out past the nuts in either situation.  I also remove the plastic housing for the connectors on the fan to reduce the amount of needed cavity space.  Heat shrink tubing works just fine instead.

Print instructions

I use PETG and take the normal settings at 0.2 layers. You can do whatever makes you happy.