Start phoning the wreckers, all you need is the harness and they can take it off an X5 in their yard in minutes if you can find one. It includes a special plug that attaches near the spare tire, so you do need the entire harness with the plug and not just the wires out at the hitch receiver.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue