My CX5 came with a Cargo Shelf as an accessory. Still in the factory package unopened. Mazda charged me the full #325 list. I will sell for $125. There isn't a picture in the Mazda accessories but, maybe on GOOGLE?
I like idea, but IIRC, it required various drilling an taping. I'm guessing it's not too hard to remove, but I need to access more of my trunk too often that this just seems, for me, more form than function, YMMV
For decades in various vehicles I've found stacking collapsible crates provide a low cost, no hassle, flexible solution in lieu of shelfs and the like. There are a number of different kinds on the market. The pictured ones below happen to fit tightly against the the lips of the Weathertech floor liner and stacked two-high still leave a good percentage of visibility out the rear window.