The 2 piece steel basin lid for the tank for the basement bath is pretty well rusted from underneath. I'm hesitant to remove it to repair it as I think it might crumble in a couple of places. It measures 20 3/8" in diameter. The plumbing supply where I bought it years ago is out of business. Google has shown some of the correct size, but not steel and not 2 piece. Any leads on a source would be most appreciated.