Okay. Not sure what all the secrecy is about- this has been done before. Alf Blake and the late Steve Webb have both travelled down this path.
There is nothing commercially available for the subject you're after. GI Joe/Action man suits are much too modern, and just plain wrong. Personally I would look at fashioning the suits from sculpting putty, when suitably painted, they will look like rubber suits, but won't suffer from perishing and trapped air won't compress as you dive (assuming these suits are going to be taking a dip).
I have some pictures of these suits, not exhaustive, but should get you on the right road. I'll post them up later, as I haven't got my camera/scanner to hand at the moment.