Backup Camera Power Connection -- Front

I've installed a backup camera + monitor (wireless) from TadiBrothers in our 2010 Prius. I have it all installed and working. The back part gets it's power from the reverse/backup light, so is only on when in reverse. I've searched high and low for a "reverse only" 12v source for the front part of the system, with no luck. I even paid $15 to get into Toyota's Technical Information System. I've downloaded wiring diagrams galore. I've discovered that the fuse for the reverse/backup lights is Fuse-19 in the engine compartment. But that fuse also covers multiple loads, like headlights and horn. Currently I am powering the front part (monitor and receiver) off of the cigarette lighter plug. But that puts the front monitor and receiver powered on even when not in reverse. I would sure appreciate any clues as to where to tap into the reverse light system, somewhere near the front of the vehicle.

THANKS!