How do you obtain a metal coat in Mystery Dungeon Red Rescue Team?

You can't obtain a Metal Coat in Pokémon Mystery Dungeon: Red Rescue Team. The Metal Coat is an item introduced in later generations of Pokémon games and is used to evolve certain Pokémon, such as Onix into Steelix.

In Red Rescue Team, the focus is on rescue missions and exploring dungeons, so there's no need for items like the Metal Coat that are specifically used for evolution purposes.