Go to the bakery at WalMart. They throw away thier used icing/flour buckets. Several times I've stoipped in and asked and they have given me 5 gallon round or more often, 3 gallon square ones with lids for free. Usually they rinse them pretty well but I always wash and disinfect them just to be sure. The square ones hold less in bulk but hold vacuum sealer meal bags better due to the shape.

