Hi amir,
Welcome to the Mattress Forum! 
and thank you for your post
If you are only looking at organic materials (regardless of whether non organic materials may be just as “safe”) and have ruled out wool or other “safe” fire barriers and you have also ruled out latex then your criteria would be very restrictive and you would basically be limited to organic cotton (such as an organic cotton futon) which may not be the most comfortable choice or perhaps an innerspring mattress that uses organic cotton or other organic fibers as a comfort layer (and these will be somewhat difficult to find).
There is a list of some futon options in post #2 here and there is also a list of some of the better innerspring/natural fiber options I’m aware of in post #4 here. You would need to check if any of them have a retailer that is near you (or that they sell online if you are comfortable with buying a mattress or futon that you can’t test in person before a purchase) and if an organic certification is important to you then you would also need to check with them to make sure that their natural fibers are also vegan and whether they have an organic certification and/or that they can make a prescription mattress that doesn’t pass the fire regulations. I have alerted one of our new members that may be able to give you a little more direction with other options you may have.
Unfortunately, In early 2018 we decided to discontinue the provision of listings of potential retailers in various geographic regions (unless they are already approved site members), because of the difficulty in maintaining such lists in a retail landscape that is constantly changing, and most importantly the confusion it was created with the consumer members who incorrectly assumed that these businesses had indeed gone through the strict qualification process and were approved as members of The Mattress Underground. Such an assumption is unfair to both the consumers seeking assistance, as well as the very businesses and manufacturers who meet the criteria to become Trusted Members of The Mattress Underground.
Good luck, this is a tough search and I hope you can find something that meets your needs.
Thank you again for your post.