I just bought an Ariens 911xxx 21-inch push mower with a Robins engine, from this eBay listing. (If you're reading this after 2007-05-31, it's probably no longer there.) According to Ariens and Gravely 21 pro manuals that I've downloaded, Ariens made two blades for the 911 series: 01137000 (Standard) 01182400 (Tungsten, 0.25 inch thick) I want to order some additional tungsten blades, but no one online seems to have them--not when I search by the part number, nor when I search for Ariens + 911000 + tungsten. Is the tungsten blade still available? If so, who sells it? Not even the third-party blades seem to be offered in long-lasting tungsten for this size (20-1/2 or 20-9/16 inches long, 3/8-inch hole).