Well, I can start you off with some websites that provide phone numbers to contact.
The California Psychiatric Association has a page for support groups. Also, NAMI California’s community services page has a form that suggests people to call based on your county and the type of service you’re looking for–it doesn’t get any more specific than “peer support group,” though.
You may find telephone calls to be more effective than a web search; even if the psychiatrist or psychologist doesn’t think their support group would be appropriate for your friend, he/she may know of one that would be a closer fit.
Best of luck to you and your friend.