I made my own ignition cut off switches for our 2002 Saturn SC2 and 2007 ION. The parts are readily available at Radio Shack and consist of a 12v-30amp two way rocker switch, an inline fuse holder, a 40amp fuse, male & female plug in type quick connectors, heat shrink tubing, one vinyl o-ring washer, plus some 10ga. wire.
I have photographs of the set-up but do not know how to post them on this site. If you send me your email address I can send the photographs to you in an MS Word file document.