There is one that I really love it is called Gelato Gradation and it is by EE Schenck. I got mine from Joy's Fabrics at a quilt show. They also have the Caryl Bryer Fallert Gradation Essentials. They do mostly shows and don't have an online store but you can see the fabric on their website
www.joysfabrics.com and then email them. The thing about the Gelatos is that they have a very fine line going through them and it almost gives it a shimmer effect - it still reads as a solid.