You are bound to find a lot of Pokémon in the wild area of Pokémon Sword and Shield. A useful Pokemon that you can locate is called Lewsor, it is a Psychic-type, which is always useful when fighting against a Fight or other Psychic-type Pokemon.
You have the best chance of locating it at these places in the wilderness:
- Bridge Field in normal, overcast weather with a 10% chance and in heavy fog with a 20% chance in the overcast world
- Motostoke Riverbank in thick fog with a 30% chance, but he won't see it in the outside world
You have a handful of options at your disposal. Unfortunately, you might have to rely on the thick fog, which you won't be able to access until you've beaten the game. You win the game by having your coach inducted into the Hall of Fame, not when you complete all eight Gym Badges. From that point on, you should be able to start breeding the thick fog in the world.
Although she's unlocked, it still takes a bit of luck to spawn randomly in the wild area, let alone a particular area. To keep things simple, you can go to your Switch's system settings and change the date to 06/01/2020. When you return to your game, you should have several areas of the map changed to Heavy Fog, giving you a better chance of locating it.
If you only want the next Pokémon evolution, Neitram, you can find it on Lake of Outrage. You need to have the upgraded version of Motisma Bicycle to cross the water, but you get it before you beat the game. Fortunately, you can locate him in normal weather at a decent chance, so that you can breed whatever you find and acquire Lewsor without having to rely on Heavy Fog.