Hi beanneu,
Just to add one more to the list that SRugs provided (thanks SRugs :))
http://www.parkplacecorp.com/showroom Larger Regional manufacturer who normally sells only wholesale but has a showroom in Greenville, SC which sells factory direct. You can see their mattresses at their factory direct online site http://www.mattresshero.com/ . You will need to make an appointment first with Jay Orders as it is not a “public” showroom.
Some comments about Colton mattress from one of our members who purchased there is in post #1 here.
These are the closest but there are many more a little further away. A list centered on Greenville is in post #2 here, around Hickory is in post #2 here, around Knoxville is in post #2 here and around Seneca/Clemson, SC is in post #2 here. The ones already listed though have some very good quality and value mattresses (a little more than Ikea but higher quality mattresses, and IMO better value and more flexible construction and layering and I probably wouldn’t go further than that). I would start with Colton and then call the two outlets near Hickory as a reference for comparable mattresses to see if you wish to make the trip.
Fire retardency is a very complex issue but it is dealt with briefly in the “natural vs synthetic” page here, more about rayon/silica in post #2 here, and one of the most informed people I know in the industry has written a very good article about wool fire barriers here.
Hope this helps.
Phoenix