Hey,
while looking for a HDMI link box for my Volvo V60, I came across a Korean company called “INDIWORK” (legally “Digiwork Factory Co., Ltd.”, it seems) which offers HDMI link boxes for different car makers and models (Audi, BMW, Chevrolet, Lexus, Mercedes-Benz, Volkswagen and Volvo).
Maybe this could be of interest to other folks, so here you go: http://indiwork.co.kr/hd-link-interface-list/
Here’s their YouTube channel: https://www.youtube.com/user/teamaudiowork/videos
Customer support has been very responsive and helpful via Facebook Messenger 
Cheers,
Wolfram