The price is ridiculous, but you should be looking to recreate something along the lines of this:
Ok, that makes good sense to me (pic below) because my upsidedown pan/cover idea comes pretty close to duplicating what we see in this pic if my pan is larger than the pizza stone. I imagine the top stone serves to capture and intensify the heat in order to bake the top side more efectively. So that would be an improvement over my upsidedown pan/cover idea. Anyway, I like the concept (pic below) and can probably build my own version for less than $25 using unglazed quarry tiles and some scrap metal I have in my workshop.
Now I'm even more motivated to buy the Weber Genesis grill because it has a lot more grill area to work with than my current grill.
Thanks for the info and ideas!