Believe me, you would not want to use styrene for United Nude, it can only be used if you cover it (it is ugly!) and I’d reckon there are shrinkage problems.
I think you need to look outside of footwear TBH, but whatever you do, get a footwear technologist involved in the entire process.
A company I worked at made a metal outsole and we did not involve a footwear technologist, big mistake - it was a disaster!
Good luck!
ETA - I’d be surprised if your company isn’t a member of Satra - I would put the question to them, when I worked in athletic footwear developing cricket and soccer, (and also when I developed the above outsole) they were very helpful, providing me with info about the right manufacturer, shrinkage/expansion rates and even the formulae for the compounds.