A free sources of buckets... deli or fast food restuarants. Most get their dill pickles and sauerkraut in 5 gallon buckets and go thru a bucket every 2 to 3 days. Most just trash the bucket and lid once they're empty. Talk to the store manager and request they save you one and a couple of extra lids.
Another source would be house painting services... with their 5 gallon latex paint buckets. This would be a bit messier proposition though.