What part of NH? On the outskirts of Greenville, Pilgrim Foods always had hundreds sitting outside, and would give them away whenever I needed one for a project. I haven't been there in 10 years, though.
There's a place in Northwood, NH that has 55 gallon drums. Lots of them at $12 each.
The place is "Barrels". They are $12 each (for now), but you have to pick them up.
Call Irene Masten at 603-942-8533
the place is just east of Rt. 43 on Rt. 106, about 200' from the Rt. 43/Rt 202 intersection on the eastbound side of the road. You'll see hundreds of barrels stacked in the backyard.
I don't know about your area, but most fish packing plants have them and love it when you take them, and the school district uses them and they may be a good sorce. Good Luck