This may be old news to some of you guys but there are 76 stations in the southland (Fullerton, Pasadena, West LA - 2) where you can get Sunoco 100 octane at the pump. It ain't cheap, about $8/ gallon, but you can mix to get your octane up to 93, etc. Ask boat owners
Not to mention specialty shops where you can bring your own container. They have the good stuff.
I know a guy who says he gets aviation fuel from the Santa Monica airport at $30/gallon
But he has an old Camaro so he's probably a liar