I restored a Quadra 700 as a gift for my wife, and it was missing three of the horizontal feet. I measured the remaining foot and whomped this up in OpenSCAD.
The original feet were rubber; this was printed in PLA with a thin rubber sheet glued to the bottom.
The vertical hook is exactly the size of the mounting slots in the Quadra case. It will fit, but you will need a bit of elbow grease.