Someone from my home town wrote in recently:

"I am trying to track down a used food-grade barrel to make a compost tumbler. Do you have any idea where to check? I really want to reuse one and not buy new. I'm in 93065 zip code. (Simi Valley) Preferably it would be one with an lid that can open.Thanks for your help.  PS I live in a small space hence the need for a tumbler. Also I don't think I'll be churning very often so I'm avoiding a bucket composter."

I grew up in Simi Valley, so I know a little bit about the area.  I have a couple of suggestions that might work:

Have you tried Craigs List?  There is one for Ventura county - http://ventura.craigslist.org/.  From a quick search, I found this listing: http://ventura.craigslist.org/search/sss?query=food+grade+drum&minAsk=min&maxAsk=max.

Another option is calMAX. It's the California Materials Exchange.  It's a construction recycling website, and while they don't always have stuff, it's worth checking occasionally: http://www.ciwmb.ca.gov/CalMAX/.  I did once see a listing for about 50 55 gallon food-grade drums up for grabs.

Also, there is also a company who makes rain barrels, compost bins and tumblers out of food-grade barrels, so you'd be purchasing recycled materials, even though it's new to you. 

http://www.easycart.net/FiresideGallery/Composters.html

It might be more than you want to spend, but if anything, it has a photograph that gives you an idea about how to build one yourself.

I would also suggest checking around the industrial area of Simi Valley - along Easy Street and East Los Angeles Avenue.  You may find something as you drive through those buildings.  Also check with some supermarkets, as they may get deliveries in food grade drums that they are willing to part with, but that might be a long shot. 

In general, most of the people who have access to food grade barrels have caught on to the fact that they are ideal for rain barrels, so it is becoming more difficult to find them at "take these away from me" prices.  It is always worth a search online, though.  Good luck and let us know what you end up using.

Thanks for writing in!