Control two different DPDT circuits with one DPDT switch
You can use a 4PDT switch, replacing the 2 DPDT switches. Or you can make your 3d case press both switches at the same time (a bar or fitting over two dpdt switches, like a large cap).

Or you can figure out the IC on the board to see if the switch is just toggling the ICs enable pin. You shouldn't need to isolate them, if you share the ground between the two. If you do need isolation then you can use optocouplers. This requires some electronic knowledge but start with pulling datasheets.