The chaps can be crafted at level 77 by using a needle and thread with three pieces of Stegomastyx hide in the player's inventory, earning 233.1 Crafting experience. Thread can be bought from the Smuggler. The hides can be bought from the Smuggler, or you can get three by killing a Stegomastyx. It is recommended to hunt the Stegomastyx because killing one doesn't always give hides. You may also receive these chaps on the table in the beginning of a dungeon.