meega solutions door mounted

A frame of metal or strong plastic that mounts on the back side of a normal residential door to hold an item that is about 8" X 10". Only need the design for the brackets to hold the item in place. I already have the drawings for the item. There can't be any intrusions into the wood of the door. The brackets would be from each side and the top of the door. Each of the brackets must be adjustable for length to fit a door from 24" to 34". I have the main concept but need drawings.