Emergency Essentials has great prices and additional price drops on Food Safe Buckets and Gamma Seal Lids. I own and use the 6 gallon buckets with Gamma Seals for my primary grain and kit storage. See my Hands on Review
For Black Friday (today 11/27/15 only) they are offering free shipping when you order $75 or more. Most offerings are also on sale.
Food Safe Buckets and Gamma Seal Lids at Emergency Essentials.More About Gamma Seal Lids and Buckets
Gamma Seal Lids are a great upgrade. You attach the base of the unit to the bucket and leave that intact. The lid screws on and off easily. No more prying lids. These are also airtight.
From the description: “These buckets are different from what you will find at a hardware store. These are high quality, thick (90 mil) food grade plastic bucket, so there aren’t harmful chemicals that may affect your stored goods.”
My rule of thumb for grain storage is 5 lbs per gallon. With that estimation two 5 gallon buckets would hold a full 50 lb bag and two 6 gallon buckets would hold a full 55 lb bag (plus a bit more).
These buckets are food grade so they could also be used as fermenters. Just pick up an airlock grommet to add an airlock. If you do that, I would go with the standard lid option, not the gamma seal option.
Also: Black Friday Roundup