I get mine from Fabric.Com although Amazon is now selling it for about a dollar a yard cheaper and it still comes from Fabric.Com. I have nothing against Hancock Fabrics, for instance, but their quality cloth is not worth using as it does not hold up.
I have also seen it in small rolls or folded pieces at quilt shows and if you google it, you will see that it is sold quite a few places now. My favorite is still fabric.com. They do not fold or crease it and it comes to me on a roll, which protects it until I can use it.