Using non-Price Pfister shower mixers on PF valve?

I’m building a new home and just found out today that the house was built with PF single handle mixer valves in the showers (I think that’s what the plumber called them). Anyway, the problem is that we’ve already ordered Sigma brand thermostatic shower mixers — no, the builder didn’t tell us — and none of Price Pfister’s shower styles match the rest of the hardware in our bathrooms (they’re very contemporary).

So, is there any sort of adapter that will let me use Sigma (or other brand) handles on the Price Pfister valve boxes installed in the walls? Or do I have to rip out limestone and sheetrock and start over?

Dave