In Pokémon Sword and Shield, looking fabulous has always been the central aspect of the game, catching Pokémon a secondary elemental at best. Who needs to catch 'em all when you can look fashionable? You're going to tell us that the second you reached a new city, that you didn't immediately rush to the clothing store? Clearly, we jest, but in the new DLC, the Crown Tundra, you're going to colder climates, so sadly, wrapping up warm takes precedent on how trendy you look! However, when you arrive at the Crown Tundra train station, you can immediately get a new accessory, the Hex Nut Sport Cap!
Hex Nut Sport Cap
To get the Hex Nut Sport Cap, you must speak to the scientist to the left of the shop; however, it's not that simple! To acquire this terrific sports cap, one must have a certain Pokémon in your team before speaking to her. In your first conversation, she'll mention a Hex Nut Pokémon, and there is only one Pokémon that fits that description. This Pokémon is one of two that can be shown; as one is the evolution of the other, you need either Meltan or Melmetal.
Update: You don't even have to have Meltan or Melmetal in your party; as long as you have one or the other in your box, you'll receive the Hex Nut Sports Cap.
Once you have one or the other in your party, go back and speak to the lady scientist, and she'll be ecstatic because Meltan/Melmetal is a Mythical Pokémon that you can't find anywhere in the Galar region, and then she'll ask to see the Pokémon. Show her Meltan or Melmetal, and as a token of her gratitude for showing her a special Pokémon, you'll receive the Hex Nut Sport Cap in return!
Thanks to PLDH on Twitter for this information!
Talk to the scientist at the Crown Tundra station if you have Melmetal in your Dex to get a hat based on it.