I built a little box made of leftover melamine and plywood (top). Has worked great so far. Doesn't smell, they haven't been able to chew out of it, and provides a lot of security for them.
Just temporary til I have enough money to buy a shed and build a rack.
I'm just going to buy one of the cheaper ones at Home Depot, Lowes, Menards or whatever. Looking for something like an 8' x 14' (so it can fit other stuff we have as well). Then I get to insulate it, yay. Should be a fun project.