ModelMaster's Marine line of acrylic paints, now out of production, were developed to the same standard as the White Ensign paints (White Ensign's may be 1 generation more direct). You may be able to order some direct from Testors, but they are now very difficult to locate at LHS or online shops.
Since you say that close-enough is good-enough, PollyScale makes some USN WWII Naval colors in their acrylic product line. Close, but not as acurate as the WEM paints. To my eye the 5H Haze Gray is too lavender, the 5O Ocean Gray is pretty good, the 5N Navy Blue is too bright.