Use your link, look below the picture of the top, where it says "Fitment and Product Details". Center of that is a bunch of wrenches and right below is an Adobe link to Installation Instructions.
Mostly worthless photos and info as you stated on the lock bar
, but I was able to see enough to figure out the build of the rack.
Honestly other then the metal bracket, the rest of the rack could easily be built out of some 2x4's, couple of pieces of scrap carpeting. Hardware and casters from Lowes/Homedepot.
Hmm, would be easy enough to fab up some stacked 2x4 sections to take place of the metal bracket. Heck use the kit to get measurements, build your own, and send back the kit.