You should be able to find a used barrel for free or at most $20, just be sure the previous contents are
n't hazardous when burned. You can use totally recycled red brick as well, and for the insulation get a big 20 pound bag of perlite and mix it with minimal clay slip to make the insulated heat riser and fire box areas. Used ducting works too for the bench, just a matter of
scrounging and making sure the proper cross sectional area is used throughout. Check Craigslist too, that's how I found the barrels and bricks I bought for mine. You can probably just get a bale or two of straw and mix it with the local soil for the cob.