Go-Goggles
From Bulbapedia, the community-driven Pokémon encyclopedia.
The Go-Goggles are a key item in Generation III that allow Pokémon Trainers to pass through Route 111's harsh desert sandstorm. Without them, when the player tries to walk or ride into the desert, they will just be turned away again. Traveling through the route is necessary in order to obtain either a Claw Fossil or Root Fossil, which can be revived into Anorith or Lileep, respectively.
Location
After the player has defeated Flannery in Lavaridge Town, his or her rival will show up and hand the item to the player, then ride off.
