I have the cheapest. I made one out of scraps from my woodshop in about 10 minutes. The factory edge on a nice sheet of plywood is extremely straight, so I cut it from that with the factory edge on the rim. The pointer in the middle is held firmly with a sprung piece of wood. No metal on the whole thing (just glued). It's even bowed a little to put the pointer between the edges, not off to the side by the thickness of the board.
