Here is a big one at Quilt in a Day. And today is 1 cent shipping!
http://www.quiltinaday.com/shoponlin...ay.asp?i=30855 There use to be a much bigger one for sale but it's no longer there. It's double the size of this one.
My mistake, this is the biggest one. I have it so I went and measured. It's 30 inches across the bottom.