A natural crib mattress? Greenwashing

I've been looking for a natural crib mattress for our second-born. On our limited budget, we can't afford to replace all of our mattresses with natural ones, but I hope that whatever new ones we purchase in the future will be natural, so that we can avoid air contamination from flame retardants in mattresses. Though the mattress industry says that flame retardants pose no danger for babies or adults, I am more inclined to listen to the skeptics and doctors who argue that the addition of so many flame retardants to mattresses may be contributing to a variety of health problems, even SIDS.

Last week I thought my search had ended, with an affordable, "green" mattress that I found at Costco, made by Simmons Kids. The package claimed chemical-free flame resistance, soy foam, organic cotton cover (that nonetheless was waterproof?), GreenGuard tested for emissions, and more. Still, I know Simmons Kids is a major retailer of standard mattresses, so I was hesitant. I kept the packaging intact and did some research. Fortunately, I found a post by Eco-Novice that linked "The Mattress Matters", a recent publication about the chemical content of crib mattresses. It's a great report on in-depth research on many crib mattresses, with a chart at the end that indicates what chemicals of concern may be present in each part of the mattresses' composition. It also indicates where the companies were unwilling to disclose what additives were used in the mattresses. It turned out that the one I had bought was probably a pretty good example of "greenwashing," where a product is made to look more eco-friendly than it actually is. Hey, it's a big marketplace, so companies will do what they can to get a slice of an ever-growing pie as parents and families go greener. In short, the mattress I had waiting probably has vinyl (as the second layer of the organic cotton cover--thus the waterproof claim), chemical flame retardants (who knows which ones), and its "soy-based foam" is probably still between 80% and 95% polyurethane foam. The company did not disclose most of the specifics. I don't trust that. Sigh. Back it went to Costco (thank goodness for a GREAT return policy!) The search is still on. I'm starting to consider getting a prescription for a chemical-free mattress... Has anyone done this?