I get my 2 and 5 gallon buckets from a grocery store that has a bakery in it. They give them away for the asking and they love it when I take all they have. Most of the time they are washed out nice and clean but sometimes there is left over frosting. The lids have rubber O rings to seal them up tight. All you have to do is ask about the frosting buckets at the bakery of your grocery store and maybe you can get all your buckets and lids free or cheap.
Good tip. Thanks!