The icons for the Armoury chest in-game, the gold-ish looking things? Those are in a unique spot.. need XIV Explorer to get to them. Inside 060000, and in the folder ui/uld . There you'll find all the icons used on the UI. The specific one you're looking for is armouryboard.tex. So! The full path to the file:
060000/ui/uld/armouryboard.tex