cmayna,
Your local auto parts store should have a switch that will work for you. there race sanctioned switches are installed so they are accessible from the outside of the vehicle and have a sort of key, or just a flip lever to cut the whole electrical system. For the short term, you should be able to find one that will connect to your battery terminal and will probably have a large screw handle, you simply unscrew the connection and your battery is unhooked. Good luck on it. the door buzzer suggestion is a good one too
Rob
