You're going to need to drive to an AZ or NV gun show. You might get lucky and find an individual that is not up on the FTF laws. I don't think that many people will risk shipping one to CA. You just missed the big Crossroads gun show in Phoenix. There were a lot of individuals selling ARs at this last show. I'm guessing that you are aware that FFL paperwork is required for lowers. Good luck.