I had a 60mm fan on hand, and wanted to use it to cool parts while printing.
This mounting bracket uses 2 standard RepRap Prusa PLA bushings, which are glued to mounting bracket.
Fan size and other parameters can be adjusted in .scad file. Most likely you will only need to change fan width and fan screw offset.
STL file is compiled for 60mm fan.
I'm not sure if one fan will be enough to cool the part (as the flow of air will only come from one side, the other side may warp), but you can always print a second mount on the opposite side of X axis.
1) Print the mounting bracket.
2) Print PLA bushings.
3) Snap the bushings on X axis so that flat side of the bushing is up.
4) Apply some glue to bushings.
5) Put the bracket on top and apply some pressure. I didn't have clamps, so I put some weight on it.
6) When the glue has set, carefully remove the mount and attach the fan with 2 M3 bolts and nuts.
7) Snap the mount where you want.