eBay has some sellers who sell pure cotton and wool futons, from 3 inches to 8 inches. One of the brands on there is Gold Bond (not related to the itchy powder) and I looked up their business's website and they appear to use chemical free fiber cleaning, but I don't know if they have added flame-retardant chemicals, which can be hard to avoid. A lot of other websites are out there with organic futons but are much more expensive - over $1,000 rather than $120-$300 (depending on size) that I have seen for some organic futon or all natural fiber futons on eBay. I have always slept better on harder surfaces, like futons.

Soaring Heart futon in Seattle is the one I know the most about. You can buy varying thicknesses of pads and futons for sleeping, or mix and match to create your own perfect bed.

Ikea also has a few natural mattress options made with natural latex, wool, and cotton. You'd have to contact the company to see what flame retardants they use though.

White lotus sells natural and organic futon style mattresses,all of which are handmade.They are in NJ and shipping is free they also have handmade pillows and the prices are reasonable.I bought a twin cotton natural mattress for about 350 couple years ago

I've heard good things about this company: https://www.tuftandneedle.com/shikibed