The old unit was tripping the RCD, an electrician found water inside the fan housing. So we need a new one! But finding a suitable model is proving difficult. 

We are looking for something with a 200mm duct (if possible). 

The old one is a triangular shape, we don't care about the shape of the new one but it's easier to make an existing hole bigger than smaller. Current dimensions are about 310x240. 

Any ideas of where to look or who we could speak to? Searching online hasn't been successful so far.