When I lived in Napa it wasn't hard to find whole barrels for $10 to $20. As the brother above said, just start calling wineries. Also call cooperages (barrel makers) for scraps.
Here's a place to start, scroll down to cooperages http://napavalleyonline.com/director...eindustry.html
PitBoss & Dishwasher, Smokin' Geezers Grill Team & Gumbo Krewe KCBS CBJ, CTC, CBBQA, ECV