They don't have most parts in stock, and if they order them in, they are generally more expensive then the ones you would buy at a VW parts store. Get to know your parts people, they are a good source for advice. You might also look into mail order for certain parts. I use California Imports , I don't know if they are any better or worse than other mail order places, but they were the only one to send me a fairly complete catalog when I requested a catalog. Also get to know your local junk yard.
Some parts are just hard to find new, especially accessories like knobs, etc.
So you pretty much have to go to a junk yard to get this stuff. I thought I had the right thread, in fact the local VW parts guy said it would work fine, but they did not tighten properly. So use the screw type, I got a set that had the washers built in, and those have done great for me. Another parts advice, that I got from someone else, that I think is worth passing on. Get a metal fuel filter, not the cheap plastic ones.