You might have luck if you include "Controllable Pitch Propellers" or "Controllable Pitch Propellers for Powerboats" in your search along with 'Variable Pitch', as that appears to be a common alternative name for them. The Quicksilver Power 2 looks like it would fit your bill. They seem to be making a slow comback with the wakeboard community. I did a couple quick searches. There are some good write ups out there and I'm sure you could find other vendors.
Here is a pretty good write on theory:
Here is one link with a guy selling them.:
I hope that helps.