I tried to search that cap in realoem.com parts catalog but I couldnīt find it.
http://www.realoem.com/bmw/showparts...&mospid=51041&
btnr=63_1069&hg=63&fg=05
Is it integral part or can you buy one and install afterwards? Because I have those same headlights without that cap and it would be nice to have those.