I have several years experience with Cromax Mosaic which is a 50 state legal solvent based basecoat and I have nothing but positive things to say about it. You can get it at most Axalta/Cromax Jobbers. Definitely in Cali. Best thing you can do is check with your local jobbers about what solvent based basecoat options they have. BASF Diamont, Sikkens, Axalta, PPG, among others, all will have something.
As for SPI I believe that sells low VOC reducers that would make the SPI basecoats legal in California. Text Barry or call SPI and they can tell you.