Cupertino will have there Asian Moon Street Fair on August 30 and 31. San Francisco will have there's on Sep 6 and 7. The Street Fairs are wonderful in that you can not only get Moon Cakes but all the little items that collect dust on the shelf (as Mrs. Yimster is alway saying, unless she is the one buying them). There will be street vendor's sell snacks and food also. Sometime you can find some real gems at these booths. So if you are not busy check them out.
Not sure of the location of Cuperatino fair (the flyer in the car and the car is in the shop) but San Francisco's will be on Grant Ave.