https://www.ebay.com/itm/BMW-Trailer...wAAOSwi3Bf7OyN
I noticed today that someone is making reproduction towing harnesses for E53s. Just thought I would put that out there in case someone wants it. I never could find a harness when I was getting my X5 sorted out for towing, which is why I never went with the OEM towing module. I may think about upgrading this summer myself.