Hi pressurepts,
It appears the @Jamesmattress has been inactive for quite a while, so it’s unlikely that they’ll monitor this discussion and answer you. Additionally, the info they provided is from 6 years ago.
Unfortunately, a convoluted ‘egg crate’ topper of polyfoam… not memory foam or latex is still difficult to find. As per the answers to your previous posts here and here on the same topic, you are likeliest to find something on Amazon or another online seller like FoamOnline
Maybe someone that found a good source of polyurethane egg-crate foam will see your post and weigh in with their findings.
Phoenix