This is an alternative fan holder for a 120mm axial fan.
Axial fans have less static pressure than radial fans so make sure you use a powerful one. Old servers and workstations are a good place to find these - the one I am using to good effect is a 12V 2.65A monster out of a Sun Ultra 20 workstation.
Print "upside down" to the STL (i.e. the 120mm section to the base plate) to minimise the amount of supports needed.