I went to
DriverGear, found a bunch of miscellaneous overpriced things to buy, printed a copy of the online "shopping cart," and took it to my local VW dealer today. Apparently they do semi-regular orders of stuff from DriverGear, so they'll add mine to the order and I'll pick it up when it arrives. It'll be a few weeks, though. (I'm ordering stuff I don't need ASAP, so I don't mind the wait. I plan to give a couple of items away as Christmas gifts.)
I've seen contradictory claims of people buying stuff directly from DriverGear. I couldn't figure out how to enter the card number on the site's checkout, which is why I went to the dealership.