You can find it very easily in Cocorico's clothing shop, knowing that logically, you should have retrieved the hylian pants in a trunk on the prelude tray. If you have enough money, we still advise you to prioritize the stealth set placed right in front of you but for a much higher amount. Cost of the Hylian set without the pants: 180 rubies.
Written by Bastien "Lloyd" Dubosq-Luyer. Translated from French by Millenium.us.org.