You can patch the hole with wire. I use the smaller wire 1/4 inch? cut a square of wire that overlaps the hole. Use a dremel or soldering iron to put small holes in the tub around the hole. Use the strand of wire that comes with the roll of wire to feed one end through the small hole and the other through the chewed hole and secure the wire on like a bread tie. This will keep you from having to buy new bins each time they start.

A block of wood might be good for something to chew on as well.