This is a case I had made (2 made, using 1) by Badger Case in Wisconsin. They custom-make boxes to my dimensions and specifications. This case as the second one is also, I use (photographer) to transport my 8"x10" prints matted to 11"x14" to art shows. This was for my spare inventory so it never went into the booth, just into my vehicle.
Outside dimension: 28"L x 17"W x 14"T
Inside dimensions: 24.5" L x 14.5" W x 10.5" tall
Closed-cell foam lines the sides and bottom, a softer open cell phone is atop so when it sets on the matted artwork it holds it in place.
Price when made was just under $400 + shipping. If interested, come see as I think you will find this box to be superbly made. The 'ball' fixtures on the corners allows you to drag the case over pavement, grass - without damage to the structure of the box or its contents. These are the same as musicians have on the corners of their boxes. These are sealed well and can be left out in the rain, or if water rises, they will stay dry.
Price is $300. Payment can be cash or credit card - either is fine.