Here's an eBay listing for an OEM E70 hitch which includes everything you need:
BMW X5 E70 Class 3 Trailer Hitch Kit.: eBay Motors (item 220511721155 end time Aug-13-10 12:14:17 PDT)

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/ / / Mike
BMW X5 Xdrive50i 2015 F15
BMW 325iC 1992 E30
BMW X5 4.4i - sold
BMW 335i X Drive 2010 - sold
BMW Z4 3.0is 2006 - sold
BMW 325is 1993 - sold
BMW 2002 1976 - sold

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