safer/non-toxic alternatives to the Pack n Play snuggle suite mattress?

I have the Graco Pack n Play Snuggle Suite on my registry. I have been looking and looking for a replacement mattress for it that isn't made of polyurethane foam. Has anyone come across one? Everything I have seen that calls itself safer has a foam core, but just a natural cover, which isn't good enough. I have been able to find alternatives for every other sleeping/playing related item. Thanks!