I bought a Z axis upgrade kit for my Ender 3 and the brackets that came with the kit to mount the power supply to the side of the frame broke within a day.  I tried getting the STL file from Amazon and they were unable to supply the file only offered a refund or replacement.  Instead of taking everything apart I decided to create the brackets I needed.  The right side bracket is modified from the picture because I adjusted it to allow for more print surface for the bolts to tighten against so it wouldn't break in half.