I'm guessing if you can figure out how to have that 3-d printed, that would probably be easier than getting someone to "part out" a capital ship. Just an idea.
This is one 3d printed source of turrets, (labelled Montana turrets but essentially the same thing). Problem is they are so pricey, you'd be better off just buying the whole ship in 3d.
I will admit I didn't dig for too long on Shapeways, so you might find another source. Years ago I recall cheaper options available. The likelihood of a spare WOTC turret out there is low, but not impossible. I heard of a couple folks that swapped out turrets from spare New Jersey minis to replace the bad looking turrets on Montana. Such a project might produce a spare turret. Unfortunately, I've got no extras.
