I'll go with the Raboesch and Cornwall Model Boats as well. That's what I put in my Smit Nederland rebuild. Easy enough to install once you work out how to scribe the ellipses that are need for the hull openings. Always heart in mouth time when you start cutting big holes like that!
With tank steering and Becker rudders, she turns on the spot anyway, but when towing, a slight push on the thruster will bring the head back round to where I want it to really point! On a single screw tug like the Rotterdam, I'd imagine that the thruster would be of even more use when turning on the spot or in slow speed manoeuvering.