If you were local to us, we would be able to ship them for you without a problem
Since your having a problem finding a box, you'll most likely have to find some junk boxes and cut them up for the best results. 28x28x10 box works good for our wheel/tire packages 18"+.
Here's a diagram from Tirerack.com on how to package wheels. This is exactly how we package ours.
-Charles@VMRWheels
www.vmrwheels.com
