FYI, I have been watching ebay for parts since this thread was started and there is now a seller that is selling spoiler assemblies for 225 that are painted and look to include the needed harness. I've also had the tapping noise coming from my spoiler so I've ordered all the parts to do the camera upgrade and hopefully fix the tapping at the same time. Managed to get the mirror for $540 and the cable for $30.
https://www.ebay.com/itm/333602342491
Excited to give this a try.