Citarella sometimes has them. A place in Chinatown on Centre Street (between Canal and Broome, on the east side--I can't recall the name) specializes in lobsters and usually has them. It is next to the Buddhist temple.
I believe you're talking about Centre Seafood, Inc. I haven't seen scallops there before, but I do occasionally find them at the fishmongers on Grand between Chrystie and the Bowery as well as the Union Square Farmers Market.
thanks everyone for your help. one more question for all of you.... i am planning a seafood feast for christmas eve and have not placed an order for fish. do you think i can just stroll into chinatown and get what i need or it will be too crazy?