What chassis battery cutoff switch do you like?

Rather than a shut-off switch, maybe using a small solar maintainer would be sufficient to keep it up even with the parasitic loads of the chassis? It depends on where you're storing the vehicle. This also works against self-discharge, which can be rather substantial in warm or hot conditions (and much less so in cool or cold ones).

For a day or a week or two, it should not be necessary to disconnect the chassis battery.