Hi jkdean,
The closest forum lists to you are for the Boise area in post #2 here and the Idaho Falls area in post #9 here.
You are certainly “out of the way” 
The only option that is local to you appears to be http://woodrivermattress.com/. They carry Simmons which I would avoid but they also appear to carry Therapedic and Restonic which may be worthwhile considering if they can provide you with the information you need about the quality of the materials inside them (see this article).
Phoenix