There are several sites which host the illustrated parts catalog (aka fiche) for BMWs. These sites are handy for looking up part numbers. They all contain essentially the same information:
http://www.maxbmwmotorcycles.com/fiche/fiche.asp
http://www.ascycles.com/illustrated_parts_catalog_main.aspx
http://www.realoem.com/bmw/select.do?vin=&kind=M&series=K59&arch=0
Oftentimes, it's handy to know the month and year your bike was manufactured(VIN decoding) to know which is the right part. That can be found here:
http://www.bmw-z1.com/VIN/VINdecode-e.cgi


