Depends on where in SoCal you are. There's a few. I think the sucker factor is that the OEM fluid is ridiculously overpriced, but oh well. Anyways, Platte Forme a.g. in Alhambra, EAS in Anaheim, The R's Tuning in Irvine. Just go to wherever is closest to your location.
Past: Toyota MR-S (Small)|Toyota Solara SLE (Terrible)|AP2 Honda S2000 CR (Rear-Ended By Big Rig)|E92 BMW M3 (Lemon Law Buyback)|Second E92 BMW M3 (Mechanically Problematic, Sold)
Present: 997 Porsche 911 (Perfect)|Mitsubishi Lancer Evolution X GSR (Impractical Daily)
Future (Planned): Subaru WRX STi Hatchback (Practicality Coming Soon)