Most of the best deals in the Los Angeles area are out of Recycler (see
http://www.recycler.com and
http://music.recycler.com/ )
You will have a pretty good chance of finding one in there somewhere I'm sure. I really can't think of any second hand stores, as most major music stores also run commercial ads in Recycler. I'd suggest you go out on a Thursday morning and grab the Valley, Los Angeles editions (and whatever other county is close to you) and chances are there will be one at a fair price.
Otherwise check the dealers listed on
http://www.synthzone.com/dealer.htm as many of them sell both new & used gear and will ship to you.