Hi Kismet,
Oops … lets see if we can get the right Greenville this time.
There aren’t as many options in the Greenville, NC area where you are but the ones I know of are listed in post #4 here. It will take a bit of extra research to make sure that the retailers listed there will provide you with the quality details of the materials in their mattresses so you can make meaningful comparisons.
The closest factory direct manufacturers to you are listed in the Raleigh thread here.
Phoenix