I've heard there's a lady who sets up in the Harbor Hospital parking lot in Torrance. There's also a guy who sells from various spots in Highland Park on the weekends. There's also apparently a woman who sells them outside the petco in van nuys that's been doing it forever, not sure if she's still there though.

Edit: these are only the ones I know about, there's probably way way more, not to mention any mexican restaurant in southern california.