It is indeed possible to get all of the amour pieces once you've beaten the game. The skimpy covers can be crafted with the Synthesis Cauldron and certain enemy spoils.
Highlight below for spoilers:
The Synthesis Cauldron can be acquired by finding the secret merchant. You can find him by travelling to the jungle, jumping down into the slug caverns, and making your way to the far side.
The hardened black sludge can be found in the valley that connects the abandoned northern settlement to the desert.