Have you checked with any of the local gas stations or restaurants? I am able to get food grade barrels here from a caterer but when I was at the gas station yesterday I noticed that they had a couple of old food grade barrels sitting outside which were used for grease for their fryers.
Check around and see if you have any commercial bakerys or bread plants close by. They usually use 55 gal barrels for their pan oilers. All food grade and they are usually used quite quickly. I used to get them from the bread plant I worked at they usually had 2 empties a week.