I'm trying to figure out what sort of "external switch" I need to use for my KLN-89B/KX-155/KI-209A installation. The 209A has the relay built in, I just need some sort of external switch. Do I really need a full-blown annunciator panel? Can I get by with a toggle switch? A Cessna I recently flew in had a simple button that illuminated GPS or NAV when pressed. I'd like not to spend $800+/- for an annunciator I really don't need.