There's another one of these I saw on Craigslist (that I didn't get screenshots of) that was 8x8 and only $500. The guy offered to load it up for free. He said it was outfitted for loading on a tow truck, too. And that box's pictures showed a fold up ladder to get onto the roof built into the front outside corner of the box
These are a little bit bigger, and not advertised for sale currently anywhere that I know of. The owner has offered me one in the past. If interested I'll ask him, so let me know