This is a modification based on this design:
I add some material to the front piece so that you can use a 1/4-20 tap to make a threaded hole in it. It will screw onto any standard tripod fitting.
I've included the back plate from the original design and renamed it to match my own version number. The original was created by VGer:
I brought the M3 bottom file into 123D Design, where I added a bottom piece to it. The 5mm hole should be right for tapping in most materials.