Where can I get an insulated box big enough to transport a tiered cake on a 16"x16" board?

People on here swear by the cakesafe. You can get large boxes at walmart or office supply stores, don't know about insulated though. Hopefully someone else on here can help

Hmm... Can I ask why it needs to be insulated?

have you thought about constructing your own? Get a big box and put some eggshells and Styrofoam around it, or even actual insulation on the outside and cover it with plastic wrap or something?