A lot of people use brute trashcans. They are foodsafe and usually available locally. I am not completely sure on the price. If you are looking for something larger, you will have to do some shopping at your local farm supply, online, or some sort of industrial supplier.
You can get food grade plastic barrels. I have 2. One is an open top and the other has 2 - 2" ports. The open top is rarer to find but much nicer for SW mixing. You can usually do a search on local for sale pages and find someone selling a few. usually in the 20-40 each range. The open top one i think originally had pickles, the 2" port one was actually for pool chlorine. Regardless I allowed time for quite a few rinses and drying cycles before either was put into use.