Hi SENCMom,
The first place I would start in case you haven’t read it already is post #1 here which has the basic information, steps, and guidelines you will need to make the best possible and most informed choices.
Hopefully you will be able to find a mattress that has the same quality of materials as your old mattress although in most cases the only foam material that is more commonly available that will last this long (at least for most people) is firmer latex.
I’m not sure where in SE North Carolina you are but there is a list centered on Fayetteville in post #155 here, centered on the Wilmington / Jacksonville area in post # 5 here, and centered on Morehead City, NC in post #5 here.
Phoenix