Looking for "joongs"
I have bought them at TC Pastry (Irving St.) in the past in the Sunset. They are generally available throughout the year but are especially plentiful now due to the proximity to the Dragon Boat Festival (June 19). Other places that are likely to have them are Mongkok and H & N (Noriega) and Wing Sing (Judah), also in the Sunset, and Good Luck (Clement) in the Richmond. FYI, type in "Joong" on the Chowhound Home Cooking Board to see how joongs can be made at home. The home-made joongs are the best as you have the flexibility of filling them with your choice of the best of ingredients. I have even made some with multiple salted duck egg yolks!