Hello Charles,
There are many companies who produce some fine models also model tug builders like myself, I have a few scattered about in various maritime museums around the UK. It's more fun but very time consuming to build yourself and a lot of research has to go into the model, it's not just a case of getting some GA plans and working from them, you need to visit the vessel, take hundreds of photographs and sit down to design your work.
Off the top of my head is this company :
http://www.scalemodelsweston.co.uk/news.phpBut many more around.
Cost of course is not cheap ! Either for a ready built or a home made model, with my vessels I incorporate full radio control, working bow thrusters, fire monitors, lights, radar ............
Look forward to seeing some more replies from other members on this topic.
Cheers, Dan.