In the old flat bottom boat series, Revell made a T2 tanker, a C3 cargo ship and an APA based on the VC2 Victory ship. Revell of Germany has rereleased them all in the last five years as the Esso Glasgow, the Hawaiian Pilot and the Montrose. They are not too hard to find or expensive. The drawbacks are that they are at odd scales around 1/395 - 1/400, and are neither full hull nor waterline, unless the ship is flat out empty. Easy fix though. But PE railing is easy to find at 1/400.
There's a really good Liberty out there as mentioned at 1/350 by Trumpeter.
A very exciting new model is the Colombo Express by Revell of Germany. Don Stauffer did a build thread about his here recently, a very nice model.
Great Lakes bulk ore carriers are available in 1/87 for the railroad modelers.
Check into card models, there are a lot of them.