Is there any concern for residual chemicals/substances releasing from the saucer being that it isn't intended for cooking?
If that worries you, use a pizza stone instead. Made for cooking shouldn't be any healt concerns.
Plus, don't know about you but I had trouble finding a clay pot base in my area, so went with the seldom used Pampered Chef pizza stone my wife already had. It sits low enough in my water pan to allow for a very greasy, long cook.
I'm pretty sure a cheaper one would do as well.I have no idea what size it is. Head for the nearest Kitchen do dad store, or search of Amazon yields many differnt size stones, and they will bring it to your door.
I should add that I am a huge fan of this method. The #1 reason I like the pan is due to cleanup ease. I cook with a pizza stone in my 18.5, and foiled over dry pan in my 22. With both I've had very long, steady cooks. I'd give the not to my 18.5 in steadier temp control, but I think it would probably be that way if my water pans were rigged the same.
I adjust my cookers manually, and never take notes. I am comfortable leaving either one of them burn over night, or leave all day while they cook.