What about the buckets that cat litter comes in? If you don't have a cat, ask neighbors or friends. Those buckets come in really handy!

How large a container do you want?
I bought some nice small containers online, but we store our 40 lb Black Oil Sunflower Seed sacks in discarded plastic 50-gallon drums, formerly used to hold soap powder, we found behind a small Carhartt clothing factory in town. We have two on our deck-one barrel for sacks of horse feed and alfalfa cubes, one barrel for sunflower seed sacks. So far, no rodents have been able to chew through the heavy plastic, or climb the sides. We leave the feed and seeds in their original sacks, and simply remove them and put in new sacks as they empty.

The barrel lids aren't airtight, so we use old blankets folded and laid across the tops of the barrels under the lids to seal out damp air and prevent mold.

I just need a container for roughly a 50 lbs bag of seed. Rodent isn't that much of an issue here. The container don't really need to be airtight either, just seal well enough to prevent insects from crawling out.

Paul

I bought metal garbage cans to store our grain and bird seed in. We had trouble with squirrels chewing a hole in the Rubbermaid type of garbage can so I bought the metal ones. They come in various sizes and aren't too expensive. The lids seal tight and keep the critters out. The silly squirrels we have here would work on the tops of the plastic garbage cans until they would get a small hole and climb in. I had a couple of heart attack moments when I would go up to get some seed and take the lid off to have these monkeys jump out after they had climbed in and couldn't get out! So, metal garbage cans cured that problem.

i use the 5 or 6 gallon plastic pails with snap on lids.
I got a half dozen from a cafe that gets bulk mayo or fruit
or other bulk. another time i got some emptys from a contractor who paints buildings. the last bunch came from a yard sale. I got 4 gallon pails of soap from the grocery store and saved the buckets. I use them to store everything from feed to flour to apples i pick in the fall to parts and even got extra pasta and cornmeal and dry beans on sale and keep the pests either in or out.

I bought mine at Lowes. The pkg came with a large and small container with a pour top and a handle. It depends how much seed you want to store. Otherwise, Bed Bath & Beyond has an assortment of containers, as does Walmrt.

I purchased the set at Lowes just mentioned,and I keep it inside near my back door, to store seeds that I buy in smaller amounts (nyjer seed, safflower).
For storing a large amount of seed, though, (BOSS) I bought one of the Lowe's store buckets (people buy them for painting, etc.). It is large, heavy duty plastic, with a handle and a very tightly fitting lid (it fits so well that it's not easy to get the lid off! But that works). It cost me about $4 and has been well worth it. I leave it outside on my deck by the kitchen door, with about 10 lbs. or so of seed in it. It hasn't been bothered once. Hope this is helpful.

Go to a local paint store such as a sherwin williams store and you can get new, unused 5 gal paint buckets relatively cheap.

For large quantities you can go to a dollar store and get a plastic storage tub with an airtight lid. They come in many shapes and sizes.

I buy my seed from Tractor Supply Co in 30# and keep the bags in a plastic trash can. The can will hold about 5 bags, which is just a one month supply here.

Any large grocery store has free white buckets that their frostings comes in. Ask in the bakery dept. and they will give to you free:)