Here is a link to the containers I use. You can't buy direct from JAZ but Racers Wholesale has them for $49 plus 10% off. I think JEGS might have them as well.
I would build a cradle out 2x4s and plywood, throw a label on the box and sleep well, knowing it would take a beating in shipping... $50 for a plastic box?? Ugh. Its a nice, use-specific plastic box though...
I put mine in a box just barley big enough, wrap the 3rd in a plastic bag and spray expanding foam around it. Once it cures I cut the excess off the top and tape the box shut. Then I put it in a 2nd box just for good measure. The plastic bag keeps the foam out of the 3rd. It made it to Oregon in a UPS truck with no issues and cost me about $5 in packing materials.