Airgas.com has 2 locations in bakersfield, Fresno Oxygen/Barnes Welding Supply may have something too. I'd reserve the Argon/CO2 mix for welding, not for beer : )
btw, welding shops typically work on a swap system. Some may do actual refills but you may have to drop it off and come back in a week. The good thing about this is that you don't ever need to buy a nice new shiny tank, just any old POS that you find on CL that meets spec. Of course if you already bought a fancy shiny tank... let that be a lesson to you : )