I haven't printed this yet, as I designed it for a friend on the Tronxy Facebook group. I've included STEP files as well in case anybody wants to tinker with the solid models.
It was designed fur use with a 40mm fan, M2.5x10mm hardware (screws/nuts) to hold the board, and M3x20mm screws and hardware to hold the halves together. If you have other fasteners or methods you'd like to use, feel free to modify the CAD files!
Also, the loops/lugs on each end allow you to zip tie the wires to the case for strain relief. It is not the most elegant solution, but it will certainly keep wires from fatiguing at the board connectors.
As always, happy printing!
EDIT (6 FEB 2018): Added a new STL for the top cover which allows the fan to be mounted inside the case. If you are OCD, you're going to hate the honeycomb grating, just sayin...
EDIT (09 FEB 2018): It fits this MOSFET.