[macmikeman]

I turned a single gang switch plate into that size opening just the other day matter of fact using my Makita "fine" tool.
and the 1/2 wide size saw bit from the bit display at the good ole Home Depot. Secure the occillating (sp) saw and turn it on and pull the switch plate into the blade , rather than trying to run the blade on the plastic faceplate, it works much better that way. For a rocker spdt for metal awnings . Looks the same size as the one in the picture above.

 

[macmikeman]

For those prices, I would take it to my favorite machine shop with all the CNC cutters and the water jet cutter. They would have it done in ten minutes and around a hundred bucks. But I got lucky and mine was set into a standard plastic plate so it was pretty easy to make the ko.