Hi ethical1,
You may be confusing some of the properties of memory foam with latex because they are very different materials and more “opposite” than similar. Latex is the most resilient of all the three foam types (memory foam, polyfoam, and latex foam) and has a much more “on the mattress” feel than the “in the mattress” feel of memory foam. Its resilience allows for much more easy movement on a mattress that other types of foam. There is more about some of the differences between memory foam and latex in post #2 here.
Latex is the only foam material that comes in a natural version and mattresses that use natural materials that don’t have any foam at all (just innersprings and/or natural fibers) are much less common and are often more costly as well than mattresses that contain some type of foam.
Polyfoam is the most common of all the “comfort materials” and is what you would normally find in the comfort layers of a basic innerspring mattress (in a wide range of quality/density levels) and this type of mattress would be common in every area of the country … but polyfoam isn’t a natural material. In some areas it’s much more difficult to find some of the more specialty materials (such as latex or natural fibers) but polyfoam is everywhere in the industry.
The better options and possibilities I’m aware of in the St Louis / Southern Illinois area are listed in post #6 here and there is also a list in post #18 here that is centered around Evansville, IN and once you have decided on the materials that fit your criteria a few calls will identify which of them may carry the types of mattress you are interested in.
Post #2 here and the sources of information and other posts it links to may also be helpful when if comes to answering “how safe is safe enough for me?” on a personal level and for those who are looking for “safer” or more natural or “green” materials in a mattress.
Phoenix