I can't find anything on this except on the BakerStone site. And they only show one size, for $170.
I'm interested. I've thought about building something for the grill. I make a decent pie in the oven, but pizza year 'round would be nice. Don't make much in the summer. Pizza season?
A wood fired brick oven isn't in the cards right now, but it's on the list.
I think this is a Kickstarter project just coming to market. Contact them for arrival dates and the larger model info. You might also be interested in this freestander, with a rotating plate. http://www.blackstoneproducts.com/index.html