Hi Painintheback,
Unfortunately there are not a lot of independent factory direct manufacturers near you.
http://www.matterbrothersfurniture.com/ They make mattresses of all types.
http://www.verlo.com/ Independent manufacturer. Their website says that they do not have an outlet near you but if you look online (for example here http://find.mapmuse.com/map/verlo-mattress-factory-stores/27.9167,-83.6075,6 ) it seems there either is or was several near you. You may need to call the closest one to see if they are still in business there.
EDIT: I checked and there are no Verlo outlets anywhere in Florida. There is also now a more detailed list for the Port Charlotte, Fort Myers, Cape Coral, Naples, FL. areas in post #2 here.
Other than these … I’m not aware of any others near you however there is always the option of using local mattress outlets that are transparent about the layers of their mattresses (or that sell mattresses where the layering and materials are available online) to test mattresses that work for you in terms of pressure relief and spinal alignment and then to “duplicate” it through a high quality and high value manufacturer that sells online.
I would avoid any mattress that has more than an inch of polyfoam in the comfort layers (including any polyfoam in the quilting). This includes any so called bio friendly or “green” polyfoams which are just regular polyfoam where some of the oil based ingredients have been replaced with plant oils. There are some local manufacturers that use much higher quality polyfoams in their comfort layers and/or will make a 2 sided mattress where these lower quality will last longer for those that have a lower budget but you will not normally see this in any of the national brands.
Basically … if you are considering a mattress with foam in the comfort layers, it should contain either good quality memory foam (for those that know for certain that they like this type of foam in spite of its disadvantages) or good quality latex foam (which is a much higher quality foam with many advantages over memory foam).
Phoenix