Years ago, my glider's panel was rewired by an owner of a FAA certified repair station / avionics shop. He used two circuit breakers as the main (and only) switches on my panel. I have two batteries and he installed two breakers. They look like the breaker you have linked to at Aircraft Spruce.

The breakers are wired so I can turn on one, or the other, or both at the same time (switching from one battery to another and not losing power to the panel.)

I must say, the extremely neat bundle of white wires, expertly run behind the panel, sure looks good compared to the rat's nest of Radio Shack stuff that was there before!

Ray