Cannon Class Destroyer

   Wow...I don't know of any fiberglass companies making anything that large, perhaps you could contact ScaleShipyard and see if they would do one by commission.  They build very, very nice hulls.

http://scaleshipyard.com/Main%20Pages/main.html

Aww, that's only 114.75"(2.91m)

Maybe if you put it in on display in a fountain along with a submarine,  and make it look like the DE is chasing down the submarine that would be cool.  You could put a water cannon between them to simulate rounds from the DE hitting the water near the sub. And pumps to simulate wake and prop wash off of each model.

You aren't doing this for the Destroyer Escort Historical Museum , USS Slater, moored on the Hudson River in Albany are you?

A Cannon-class DE was 300 ft long (LWL) and 36'10" wide.    In 1:32 scale this works out to 9.25 feet long by almost 14 inches wide.   That is a very large project.

A one-off commission build from a fiberglas hull company would likely be a very expensive proposition.  You would end up paying all the R&D costs which the company would then amortize againwhen they put your hull in their product line.   You would essentially get shafted.   Consider a  fiberglas kayak (of similar size to your project) is several hundred dollars -  and the cost has been amortized among other products.   In addition, cost and effort of scratchbuilding the superstructure and all the deck fittings could lead to a life-long project. 

Is the subject of your diorama the ship or is it a piece of action which is associated on or near the ship?   If it does not pertain directly to the ship itself I think I'd rework the focus to center on the other subject and have the ship as a background.   Use a shadow-box method to force perspective.   Use only a section of the hull as a backdrop.