That's a good point Saker, that 'Unused' "Auto-dimming mirror" function power supply line may be there. But the OP will need to be 'extra cautious' with this application due to the use of "Ground side switching" technology and "ECU circuit management". I know that ground-side switching is just as simple as 'Conventional scheme' types, but it's also just as easy to get the wires crossed up as well, and one mistake could be the cause of a catastrophic chain destruction phenomena e.g., "...I must have accidentally mistaken the "HOT" wire for the "NEG" one because when I reconnected the battery I heard a noise come from the "Upper Center Console" followed by flickering Instrument Cluster warning lights and then..."
"I hope no one here ever has this actually play out!"
Rgds!