Well, the Boise area doesn't have as much as many other places but it does have a few I have on my list that may help. Bear in mind that I don't have every retail outlet on my list so some of the smaller retail outlets in Boise may also be worth calling to see if they sell latex. There are about a couple dozen stores in the general Boise area. Here is what I know of ...
http://www.furniturerow.com/locations/locationsByState.jsp?state=Idaho Manufacurer. They have two mattresses called the Aspen and the Snomass that are "mostly latex". They both have an inch of poly above but they will give a general indication of what latex feels like and would be worth testing.
http://www.ashleyfurniturehomestore.com/storelocator/storelist.aspx?countrycode=USA&country=United%20States&statecode=ID&state=Idaho&city=boise Manufacturer. They also have some latex mattresses mixed with poly but I don't have as specific details about their construction. May also be worth testing but would need a bit of research to find out what exactly what was in their layering (they may and should also tell you this)
http://www.isleepwithgrace.com/locations.htm Retailer. They carry Englander, IBC, and Restonic which all could have "significant" latex in them, particularly the Englander and Restonic (The IBC has more than an inch in the top of their "latex" mattresses). Also worth going to.
http://www.heavenlybedrooms.com/ Reailer. There is a heavenly bedrooms in Boise but I don't know if they are connected with this one in PA. If they are (and are still in business) then they would likely carry Ecosleep (Gold Bond) latex mattresses which would be a very good testing ground as at least one of them would be all latex.
http://www.evertonmattress.com/ Manufacturer. They carry Restonic and also make their own brand and may have an outlet in Boise (they are based in twin falls). Would be well worth going to if they are close enough.
This not be as much as other areas but should be enough to give a good indication of what latex feels like.
Good luck
Phoenix
This message was modified Dec 29, 2010 by Phoenix