Keep looking, they turn up, but it sometime takes awhile, and you may need to travel a bit to get what you want. Spend some time reading threads here and you'll be an educated consumer. Do note that its become very hard to find OEM trailer hitches, at least for E53s [01-06]. The aftermarkets aren't good for hauling much of anything [most agree ....], so you'll want to look for one equipped with an OEM hitch if you don't plan to roof mount the bikes. Some of us here are advocates for the manual transmission versions [only the 3.0L], but they are quite rare.

__________________
2006 X5 3.0 6-spd w/Evo UUC ssk
sport/premium pkgs
born Valentine's Day, 2006.