If you have the space, go to a hardware store or a farm/feed store. Buy metal trashcans. Use bungie cords to secure the tops. For more more security you can secure the tops with metal pipe strapping and a few bolts. As long as you keep the bottoms of these cans away from moisture, they'll last for years and years. Rats and bigger critters can't get into them, if you have them secured properly. You can make gaskets for them fron auto innertubes.

Lee