This is a parametric power strip holder. Click the link in the description to use Onshape to make your holders. You can fiddle with the settings in the top left to make any size of electrical strip holder you want. Check or uncheck the “wire hole” setting to allow for wires to pass through or not. You should make one for each end of your strip.

This is important: THE TWO ENDS OF THE POWER STRIP ARE PROBABLY NOT THE SAME SIZE. I learned this the hard way. Even if it looks identical, its probably off by several millimeters, which is enough to make the bracket not work. Get calipers and measure both ends very carefully. I have no idea why one side is bigger than the other, but it is on all strips I tested.

I found 2mm to be sufficient for shell size. 3mm is quite stiff. 

Make sure you use drywall anchors if mounting in drywall.

The 2 stl files are generic examples and probably will not fit your power supply. You should follow the link to Onshape and make one that fits your power supply perfectly. Power strips are not universal for some reason.

If you set the wire size, wire diameter, and overhang to be large numbers, you can create a mid-strip holder. This is useful if your power strip is not using right angles. You can see an example in my photo.

[https://cad.onshape.com/documents/a17261f1388944bed7b19437/w/17dcf347174a826eb058698f/e/d5c3407d5d5f09ec9fad3ce4?configuration=height%3D0.028120000000000003%2Bmeter%3Boverhang_width%3D0.002%2Bmeter%3Bshell_thickness%3D0.003%2Bmeter%3Bwidth%3D0.039369999999999995%2Bmeter%3Bwire_diameter%3D0.01%2Bmeter%3Bwire_height_from_base%3D0.0174%2Bmeter%3Bwire_hole%3Dfalse&renderMode=0&uiState=68f6cbd36494637069a51216](https://cad.onshape.com/documents/a17261f1388944bed7b19437/w/17dcf347174a826eb058698f/e/d5c3407d5d5f09ec9fad3ce4?configuration=height%3D0.028120000000000003%2Bmeter%3Boverhang_width%3D0.002%2Bmeter%3Bshell_thickness%3D0.003%2Bmeter%3Bwidth%3D0.039369999999999995%2Bmeter%3Bwire_diameter%3D0.01%2Bmeter%3Bwire_height_from_base%3D0.0174%2Bmeter%3Bwire_hole%3Dfalse&renderMode=0&uiState=68f6cbd36494637069a51216)