-After completing the Goron Temple and freeing Hyrule from the Twilight, go to Castle Town. Go the southwest side of the town square and ender the building with a Goron standing there. Talk to him and he will tank you for saving their mines. He’ll then offer you a Hylian Shield for 120 rupees.
-The store in Kakariko Village sells the Hylian Shield for 200 rupees.