Moda Bella and Kona solids are less expensive than regular quilting cotton (usually about $7/yard instead of $12-$13/yard), and once you know which manufacture number you want, you can buy more and be assured that the dye lots will be the same. I have done this with Moda Bella black and white bolts.
I've seen bolts and half-bolts of Kona on sale at Fabricdepot.com. Usually they offer red, white, and black. You could check there.