Unless you can find a wrecked rig getting parted out, that actuator is not sold seperately. That entire unit mounted on that bracket including the 3 cables is sold as one piece.
PN: 15926027
CONTROL. End Gate Lock
CONTROL,E/GATE LAT(INCLS CABLES,ACTUATOR,LEVER & LATCH). Required: 01For: N2(06) LIFT GATE W/GLASS(E52) (2003-2009)
$320 retail... Best prices I've found below-
http://www.google.com/products/catal...d=0CC4QgggwAA#