In my vast Thomas Train-buying experience, I have found that allaboardtoys consistently has the best available prices. Find a wooden Duck character there for $11.00 now, or on sale for $8.77 - that is really cheap for a wooden engine. Duck is also available battery-powered, for $19.00 or less.

Duck is a smallish green engine with the letters GWR on his side. He's not a really popular engine, but he is unique looking. He is my son's favorite sandbox train for some reason.