Hi Mike in FL,
Once you have tried some of the other suggestions in the first post I linked, if you decide to add a topper then post #2 here and the topper guidelines it links to have some suggestions that can help you use your sleeping experience as a guideline to help you choose the thickness and firmness of a topper that has the best chance of success. It also includes a link to the better online sources for toppers that I’m aware of.
Phoenix