Hey Dennis!
The Battery Disconnect uses a Latching Relay. One 12VDC pulse takes it from Off to Locked On. Next takes it from Locked On to Off. You could do this with a doorbell button.
Our Jayco has a momentary contact switch marked ON and OFF. It's spring loaded toward Center. However way it's wired, pushing to ON **OR** to OFF pulses the Disconnect to whichever position it wasn't in before being pulsed.
Ours looks a lot like a Carling Switch shown
Here on Amazon.
If you want to post a pic, I'll try to help farther. Can take our switch off to look at if needed.
Dennis, and others watching at home: BEWARE! I've seen two distinct types of Latching Relays, and they require different control wiring.
One: As I described, where the same polarity of 12VDC pulse toggles the Disconnect Relay contacts between OFF and ON. Needs just two wires and a two pole momentary switch.
The Other: Direction of Toggle is determined by the polarity of the pulse. Say it has Black and White wires. If Black is (+) and White is (-) then the Disconnect is pulsed ON. Pulsing it the same way again will leave it ON. If Black is (-) and White is (+) then Disconnect is pulsed OFF. Pulsing same way again will leave it OFF. Needs a Momentary switch with more terminals, connected to more wires.
I think ours might have once been The Other, and the Disconnect was replaced, then rigging its switch to cause a pulse in ON or OFF.