Or go to your vet and ask for one of the styrofoam lined shipping boxes they recieve their drug shipments in. I get a lot of them from my vet, and I've asked at pharmacies as well. That's free AND recycling. The drugs are all sealed and contained, so you won't have to worry about contamination. And those boxes are way sturdier than a box with seperate panels of styrofoam, which is sturdy itself.