If you require international stamps or commemorative designs, a main post office or a specialized stationery shop like Paper Source is better than a general convenience store.
Multiple locations throughout the city, such as 2370 Market St and 236 West Portal Ave , sell USPS stamps. Mailbox rental service ClosedSan Francisco, CA where to buy stamps sf
A long-running local option in the Castro that provides shipping services. Glen Park Mail Depot Mailing service ClosedSan Francisco, CA where to buy stamps sf