New Post: How to get reference of the domain type from other Module (Asssembly) via loosely coupled way?

Could you elaborate on why you don't think these are good solutions?

The problem you describe is independent from Prism.
You will have to reference another .NET assembly to use a type in a, dependent, assembly.
There is no loosely-coupled way to do this AFAIK.

Additionally separating the interface from the implementation is a good thing.

jan