Hi melvy1983,
The better options or possibilities I’m aware of in the Allentown/Bethlehem/Easton areas are listed in post #6 here.
You will need to check their websites or call them to find out which of them carry latex toppers that you are interested in testing and I would also try as much as possible to test their toppers on top of a mattress that has a very similar firmness level to the futon you are sleeping on so that you will have some sense of how the topper will feel on top of your futon.
Phoenix