In addition to Keepsake, Hancocks, and Marshalls Dry Goods, I've bought beautiful backings at Fat Quarter Shop. It was during a Black Friday sale last year. The backings were rich in color and design and a good price at the time. May be a good place to watch for sales. Missouri Star also had some great prices on quilt backings during their Pre-Christmas sales. I bought a couple from them too and was not disappointed.