Hi justakin,
Unfortunately you are on a very difficult quest and outside of actually trying another mattress that “feels” similar based on your own experience the only way to predict whether another mattress would “feel” the same is by knowing all the specific details of all the layers and components in the mattress you purchased and then choosing another mattress that had exactly the same layers and components (including the cover).
There is more about the different ways that one mattress can “match” another one in post #9 here but trying to “match” a mattress based on more subjective perceptions would be a lot like trying to match a recipe based on very general descriptions like “it was a little bit salty and had a crispness that I liked and had a smooth but chewy texture” without knowing any of the specifics of what was in the recipe and would be nearly impossible without a lot of luck.
If Future foam wasn’t able to “match” the mattress that you purchased then it’s unlikely that anyone else could either without much more specific details about the materials and components in the mattress you purchased. Based on your description it’s quite likely that the top layer was some type of gel memory foam but there are so many types of gel memory foams that each have different properties and because all the layers and components in a mattress will affect how the mattress “as a whole” feels and performs that this by itself wouldn’t be enough to be able to “match” the mattress.
You are probably referring to buckling column gel. You can read more about this type of material in this article and in post #2 here and post #2 here and the posts and topics they link to but it’s very unlikely that this is what was in your mattress or any mattress in this budget range.
Phoenix