Most of mine were missing or broken, so ordered from Vagparts.
They sent me plugs and retainers.
I tryed to put new plugs into old retainers. Pretty tricky, very tight to get into lock position.
I ended up removing old retainers, with sharp bladed screwdriver.
I reatached new ones with strong adhesive, then covered with underseal as before. New plugs locked more easily.
rs2315.