I used to make enameled switch plates, and would cut my own out of
copper. Rarely did I use the regular rectangle shape, but would cut
them in ovals, or circles, or freeform.
To assure that I got all the holes in the correct places I made
templates from a regular commercial switch plates, and carefully
scribed onto the copper, the openings to be sawed, or in the case of
the screw holes, to be drilled. It was labor intensive, but I was
able to get the shapes that I wanted, and was able to make plates
with any number of openings.