Should be able to get one from a breakers.

It's located half way down the left hand side of the radiator at the front as you stand in front of the car & has 3 small rubber vacuum pipes connected.

Problem is more likely to be sticking turbo vanes, leaking vacuum pipe or boost pipe back to the ECU blocked with oil.

Do a forum search on overboost or limp mode & you will find lots of similar posts.