I recently found myself on an un-air-conditioned streetcar in 35C weather, and knew the solution involved melting some plastic. Voila.
It's all parametric. Download and print the examples here, or generate your own fans using the included OpenSCAD file. Don't be intimidated by OpenSCAD-- it will take you less than 5 minutes to figure out how it works!
Add texture to your fan with holes (using a 3rd party application -- the exampled pictured was done in Tinkercad).
For an even better look, change the filament color after 0.6mm. The blades will be one color and the arms another.
Make sure you have a Bottom, Mid, and Top file for the same fan. The suffixes tell the fan's dimensions:
r = mm length of fan arm
b = % of fan arm that will have blade
a = angle (arc) of each fan blade
c = count of blades
s = position of slot-notch that holds blades to each other, as percent of fan arm radius.