Hi cathy,
I would personally avoid Sleepy’s if at all possible because the odds are very high that you won’t be able to find out the materials that are inside their mattresses. Enso tends to use lower density memory foams (less than the minimum 4 lbs I would suggest as the minimum density memory foam I would consider except perhaps in a layer that was in the range of an inch or less). The Gemma doesn’t list the details of the materials inside it except in generic terms. The “gem like” foam is just reticulated or fast dry polyfoam which as they mention is often used in outdoor applications but is often used in thinner layers inside mattresses to help them ventilate (there is a good description here and they are very open and breathable and usually quite “stiff” and will allow water to go right through them).
Post #4 here may be helpful and includes some of the better options or possibilities that are in reasonable driving distance of the Kingston, NY area.
Phoenix