Organic Materials

Hello there. I haven't been to this board before, as I really don't know how to sew, but I have decided to try something. I would like to make an organic futon-type thing to go over top of the mattress my dd sleeps on. I can't afford to buy one already made. I have found some places to buy organic cotton fabric by the yard fairly cheaply, buy haven't had any success in finding anything to stuff it with. Any ideas? I do not want to use wool, so it would have to be cotton or hemp (or another natural material I am not aware of).

Thank you