Here is a model of the wemotec 90mm midifan, done in Rhino. I have also saved it in a couple of other formats (iges, stp) which I hope some will find useful.
The model is done following the sketch I have attached, so best case senario is that it is as accurate as that sketch. In general I think I have kept the overall dimensions quite accurate (inner - outer diameter, length, motor mount diameter), whereas in other areas (blades of the rotor) the approach is mostly "free form".
All in all I think the model is good enough for illustration purposes (see how it looks or how it fits in your model).
Hope you enjoy