Okay, sign up to be a volunteer at a hospital or clinic that requires you to have your immunizations. Then they should offer the immunization to you for free, as it is required to work there.
The hospital I worked at required immunization records for ALL hospital employees, even volunteers. As a result, they gave out the Hep B shots for free to those that didn't have it already.
Maybe it is a CA thing, I don't know because California required Hep B for EVERYTHING now days. The student health center at my school gives them out for free because it is required by the state for all students to have it upon entering college!