For those who don't already know, like me who just found this :-) ETKA is an illustrated parts catalog for Audi/VW and others. You have to register, but it takes about 10seconds.. and doesn't cost anything if you are in the US.
If you are looking for a part to our cars, it should be in there. This will help you find a part number to take to the dealer and order the correct part. You can also order parts direct from this site if one chooses.