So...are you trying to avoid piecing a backing? If not, just go with what's on sale, or scraps that you already have. You can even make it more colorful by using several, smaller pieces of different fabrics. I like Marshall's, Ebay and Connecting Threads (On Sale) for the inexpensive stuff. I'm also with the "sheets camp." I use sheets in my own, utility quilts for my home and have never had a problem with wear, or with stitching through them by machine. Most sheets that I use are 100% cotton and of medium thread count. I sometimes find good ones at the thrift store for just a dollar, or two.