I had to do a Google image search to see the back. So this is merely a way to switch off a plug-in device without unplugging.
So, you're looking for a 120/240v, 50a plug, 50a socket, and 50a 2-pole, switch all in a self-contained plug-in enclosure. :jawdrop:
In my opinion, you'd be better off wall-mounting a switch by the receptacle.