I have seen several battery cut of switches installed in DeLoreans. I have never been impressed with the bulk of them currently available. I have since come across the Master Disconnect Switch from Pollak. It is a heavy duty and sturdy switch. They have been manufactured for years, originally being made in the United States. They are now being manufactured in Taiwan by Pollak. I have recently come across a stock of USA made switches and am offering them for sale here. Comes with switch, custom made mounting bracket, and battery cable.
Please see my article on DeLorean Directory for more info: