Here is a square cornered version of the nintendo cocktail cabinet glass clip, This was made to fit my Nintendo Space Fever cocktail cabinet. The originals are fabricated out of steel and chrome plated. They are hard to find nowadays and as far as I know, no one manufactures them.

I made them as a prototype for me actually making them out of aluminium (I am a cnc miller)

They fit really nicely and work ok, but I wouldn't trust them holding heavy glass if the cabinet was being jostled about.