I got some from Etsy a month or so ago from Official Yeti Forge, but haven't used it yet. They had multiple sizes and I got 5, 10" pieces of 1.5" diameter.
I also picked up 3 pieces of 1 1/4" and used 2 of the 3 so far from High Temp Tools. I do it by hand only, but I got a 1/4" thick, 7"...