I got mine off Ebay. They were $150 and just about new.
There was a guy in San Mateo California advertising on Craigslist for $250 new. That was a couple weeks ago so they may be gone.
If you do get them used make sure the front leafspring eye bushings are good. They are made out of aluminum. If they are deformed from removal etc. It will either make the bars not work right or be a pain in the a$$ to press them in. The bushings are around $40 from Caltracs. You can buy them directly. Same thing with the Caltrac bars. They will sell them to you directly.