Nikon 'forgot' GPS/BlueTooth on D800...

There is the Unleashed D200+, Bluetooth adapter.
http://www.foolography.com/products/unleashed/
It is quite smaller than AOK-4N

But I agree, GPS should have been integrated into D800, or at least into the expensive MB-d12 battery grip together with radio triggering of the camera to add some customer value for that outrageous price.