Call some of the companies listed:
List of CO2 fill locations in SoCal
Welding supply places or medical gas would/could be able to do it.
Josh, a lot of places will not fill on site and if you're like me, you wouldn't want to leave the tank there overnight. One of the things I was thinking about before you guys gave me the tank was to simply buy a used tank and just add the Powertank hi-flo regulator. You can find used tanks very often on Craigslist. I've found 2 10lbs for $45 before. Deals are out there.
I would keep the compressor as a back up.
