Looking for battery disconnect switch recommendation

Check out marine supplies, lots of options. West Marine online, if nothing else around you. Made to be in a salt water environment and can handle voltage, amperage and the elements, plus keeps the batteries isolated. Used one for years and just like you mounted to the side of a battery box. Don't buy cheap, you get what you pay for. Perko is a good brand, amongst others.

However, if I did it again, I think I would mount it in a forward compartment, so I could have it in a locked location.