You will find sources for 3.5, 4.25, 5 and 6 gallon buckets. Make sure you only buy buckets that are FDA food grade certified if you want to put food stores in them. I personally recommend more smaller buckets than fewer big buckets because it allows you to better break up your food stores and the smaller buckets, when full, weigh less so are easier to handle. JMO
BE VERY CAREFUL OF HARDWARE STORE BUCKETS!!! Many of those are made from plastics that are not food grade/inert and should NOT be used for food storage.
I've gotten most of mine from resturants free for the asking, be forewarned pickle buckets take forever to get the smell of vinegar out of though, icing buckets from bakeries are the easiest to clean & reuse.
All so try groceries with deli's, my wife works at a Marsh and we get all the 5 gallon food grade buckets we want for free. You just have to clean them out a little.
Believe it or not, if you go to Walmart, into the paint department, there are 5 gallon buckets and lids. They are made by Encore Plastics Corp out of Byesville, Ohio. The buckets cost ~$4.50 and the lids are another ~$1.50.
Not knowing whether or not these were food grade, she called the company and they stated that all of their white buckets which are Plastic #2 are indeed food grade and are the same as the ones used for pickles, frosting, grain, etc.
So now there's no need to purchase from expensive websites and pay all kinds of shipping, just stop by Walmart and head over to their paint department.
Do you think there would be a problem using the buckets from menards, with the food being in vacuum sealed bags? That's what I've had for ages, with gamma seals.