We had some small outdoor garbage cans, I'm guessing in the 25 gallon range...and the bottoms were wearing a bit too much to use them for garbage hauling. I cleaned one of them carefully, drilled four 1" holes near the bottom on the side, used fender washers and short screws to attach one lid to the bottom of the bucket so that the lip of the lid would contain the food, and used another lid for the top. It easily holds 50 pounds of feed.
This method can attract rodents to your coop. So be sure to plug every nook and cranny where rodents can enter and monitor regularly. I have set a number of mouse traps around the coop where the birds cannot get to them and have yet (after 6 months) seen any evidence of rodents in the coop. I do sprinkle scratch in the run and have seen the girls chase down and consume mice out there. So I don't think that mice would stand a chance in the coop either! But I would rather not deal with rodent droppings while cleaning the coop.