Help for new guy, 12 volt Q

I want to eliminate the ignition switch on my car. I am going to toggle the ACC (or I) position, I want to use the Cruise Control button for the IGN (or II) position and am going to use a late-model starter button for START. All of this will be relayed, of course.

In reference to the IGN step, I need to know the name of the component that will take the momentary voltage supplied through the cruise control button and keep the relay supplied with power until I turn off the toggle switch.