https://www.etrailer.com/Custom-Fit-Vehicle-Wiring/Lexus/LX+570/2014/HM11143910.html?VehicleID=201431285
The wiring is all there, you just need to purchase each end. Rear end part is link above.
You can use RedArc like lx200inar mentioned or other brake controllers. There is thread in MUD how...