Unglazed quarry tiles. If you get 8x8 and use four they’re a good size for a 13” pizza, easy to stack and store when done. Work great. Lots cheaper.
What keeps them from sliding around?
I saw tiles used on “America’s Test Kitchen.” Outset makes Pizza Grill Stone Tiles, in a set of 4—8.27” x 8.27” sold by Amazon for $30. The handling and storage of them is much more convenient.
However, “America’s Test Kitchen” also said that “steel stones were a better heat conductor than ceramic, so baking steels “throw” their heat into doughs much faster, causing them to rise higher and bake and brown more quickly than ceramic baking stones do. The crusts produced on the steels were just a bit more on par with those produced in a professional wood-burning-oven pizzeria: supermoist, with a tender, chewy interior and a crisped, charred, flavorful exterior.”