I had a BMW with a Bosal hitch, nice quality. After visiting their page, click on products, then hitches to see an example (generic shown)
http://www.bosal.com/BIM/index.html
Here's a retailer's page for several brands:
http://www.kupplung.de/
Do a search for Anhänger or Anhängerkupplungen or AHK.
MarkC