Where can I get Metal Babble Armor?

First, you'll need the Magic Key. In Endor, there's a shop in the southeast corner where you can buy Metal Babble Armor for 15,000 gold. Also, you can get to the treasure chests by opening a secret door in the castle, climbing some stairs to the top, and then jumping off the tower. You'll land on the roof of the hidden armor shop.

On the first floor of the castle, open a hidden magic key door. Beyond it you'll find some stairs.