A safe bet for your Powerex mast would be a Simmer sail. A 2XC 7.8 would be a good fit, As would a VMax 7.9. Both are designed on 460 masts.
Your Powerex mast is likely to be too stiff in the top (i.e. too average in bend curve) to fit a Neil pryde sail well. The Ezzy might be a better fit.