Gift: Route 8
You won't find Shieldon in the wild in this game — you get it as a gift.
Looking for Bastiodon? It isn't found in the wild in this game — evolve Shieldon (Level 30).
For the look, the best colour match is Ultra Ball or Heavy Ball.
Evolution: Shieldon → Bastiodon (Level 30).
Shieldon in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)