I found this extensive list of Alfa Parts Suppliers on AlfaBB.com. There were some usual suspects, but also a number of smaller vendors I had not heard of before. I figured I'd post the link to the list here in case someone is looking for some "crossover parts". Over the years I've found a bunch of odds and ends for Ferraris and Lamborghinis at Alfa and Fiat vendors for much less money.
Centerline is at the top of the list, but I'd mention in this case that "prominence" on the list is not indicative of "quality".
http://www.alfabb.com/bb/forums/anythin ... -list.html