Start using up some of what I have here. I need to do that anyway. Would hate to think that some day(when I ain't here) someone bought it all for a few bucks.
I use a lot of sheets, they are 50/50 polyester/cotton. The 200 count flat twin size ones are $4.00 at W_M You get a lot of material in one of them and they come in many colors and stripes also. They have better quality ones too, but I read where 200 count was better for quilting.And the good thing, if you use them for backing there should be no seams.