I can't think of any one shop off the top of my head... but right around Nob Hill is the Shopping district a la Powell and Market. That's more general shopping, but you'll find the Westfield Mall and Union Square, with various clothing stores, coffee shops, and places to eat in-between.
Going up Powell (toward Nob Hill), you'll run into Chinatown, and then Fisherman's Wharf at Pier 39. Both of those places would probably have a few shops up your alley.
Much further west from there, near Golden Gate Park, you can go to Haight St. with tons of miscellaneous shops and street vendors that sell all kinds of things. In the same vein as Haight, you could also catch BART (bay area rapid transit... subway thing) to Downtown Berkeley, and walk around Telegraph Ave.
Best of luck in your search, and I hope you enjoy your visit.