Are you talking the "Maximillian" plate armor (or AD&D Full Plate, if you're into that)? That would be a tall order (and if you're looking for the even less mobile Jousting Armor or Field Plate that would be even tougher, as it is not symmetrical). The closest thing I've seen so far is Ghosts's knight, available at Greylight Poser and the Props Guild. This character is in more stylized Plate Armor though. Though (now that I think about it) I do have an image of something like this done by a "Dr Legume" in Bryce - I'm not sure where Dr. Legume got the model though...