This is a remix of Burblifetech's remix that includes the cover, but I'm including the original as I've tweaked it quite a bit for aesthetics.
I basically remodelled it from scratch so that I could make ones of different sizes easily. It isn't printable as a modular piece, but I can export an STL of any size. I changed the fan to a 120mm as that's what I had laying around.
I've included one that can fit 3, 4 and 5 rbpi's, and I can make any other if someone needs. Or if you need different fan size, I could do that too.
Printable without supports.
__Update__
I've added two more of the 4x stack, with extra heigh clearance for each unit. It adds above each Pi, so 32mm total added Z height.
__Update 2__
Added a 3x stack extra height cover and one 3x stack module that fits an 80mm fan.
__Update 3__
Added a 92mm 4x module.
The author marked this model as their own original creation. Imported from Thingiverse.