Looks like the aftermarket is finally catching on. Hayman Reese have their towbar with smartclick wiring for the WK2, and now Milford has a cargo barrier too ...
Rhino have also introduced a new leg set for their HD and Aero HD bars that fit the captive nuts in the roof rail of the WK2 GC. Hopefully these will also work with their Alloy and Pioneer trays and platforms.
The Rhino instructions are dated 21/03/12, but they appear to have become available in the last couple of weeks.