Try overstock.com. they have odd pieces, sometimes solids colors in 250 to 300 thread counts. Mostly what I do, I buy the sets, don't seem to wear out the top sheets, so use them when I can for backing. I like to use the ones I have used and washed a lot as they are softer and easier to quilt. But I have used new ones occasionally but find the denser thread counts are hard to quilt.