Computer Cases For Sale

As perhaps 20X20X8 or something like that? I looked at Office Depot, Staples, USPS does not have this size and not a UPS store. I am perplexed! Each time someone buys a computer case comes the case in such a box if anyone is to go somewhere, but why can not I find them on sale everywhere!

Try instead of renting U-Haul. They have shipping boxes and packing stuff.
Or the Uline catalog. They have a very wide range and I think an online store as well.
Or search boxes for shipping. "There are probably many.

My favorite carrier for cans is Uline.com