The California FasTrak pass can be purchased by mail, online at the FasTrak website, or at a number of retail locations throughout the state. Many Walgreens, Safeway and Costco locations in the San Francisco Bay Area sell the passes.
As of March 2015, the FasTrak website has an interactive map that shows the addresses of stores that sell passes. Nearly all of the Walgreens stores in San Francisco and Oakland sell the passes. They are harder to find as you move away from the Bay Area, but some Costco stores in Sacramento and Tracy sell them. In the Los Angeles area, FasTrak is linked in with the Metro ExpressLanes system.