You can find them that large but they are going to cost you. If you look on Amazon there is a Chinese import company that makes one pretty big but I have heard nothing but bad reviews for them. As far as a name brand (Griswold etc.) in the 20 inch range I have seen them sell for $200-$1000. When I bought that large group of skillets I mentioned above it came with a large skillet however it is not cast, it is some type of steel. It has a tag on it and was made between 1950-1970. It is about 24 inches. I am waiting to clean it up like I did the others but it should be treated the same as cast iron, stripped down, seasoned, and then ready to use. Here is a link to the pics I took of the load I bought and how well they cleaned up.
PS they are for sale if anyone is interested.

http://s823.photobucket.com/albums/z...20restoration/