I used a cage like that for awhile. You can go to Wal-mart or to your home improvement store (Lowes, Home Depot) and ask for zip ties. In fact the Dollar Tree also sells them. They are plastic strips with a hole at one end and little teeth on the other. When you stick the end through the hole and pull tight the teeth catch the hole and hold. Once in place you have to cut them off with scissors. Reinforce all of the sides with those. Use a few per side since your chinchilla could find them and chew them off. We never had a problem with that as long as we were careful to cut the end off of the zip tie after it was fastened. Place wooden shelves going both front and back and side to side. We alternated ours. (Lower level front to back, middle level side to side, ect) Once you do that the cage should be plenty stable.
