They have the U-Boats for the floating floor, but offer nothing to go under the stud walls.

I'm looking for something like this:

The Studiospares stuff is what we've used for a couple of builds and seems great - it's 50mm, so two needed for the usual 75 or 100mm sole plates.
https://www.studiospares.com/ProductDetail.aspx?p=406070

There is no benefit to decoupling a wall from a cement floor. Attach the footers using standard concrete anchors. Save your money for adding mass to the walls and decoupling the ceiling from the existing one. A cement floor is not the weak link in the assembly. Its more massive, and has a lower resonant frequency than the walls will have.