Where to find the Dubious Disk in Pokémon Legends: Arceus

gamepur.com:

As Pokémon Legends: Arceus holds several items returning from past games, the rare Dubious Disk is one of them. As expected, this mysterious object only has purpose and it is a crucial one for trainers who are looking to truly catch them all. In spite of this, the disk is a tough find and can only be found by doing one of two activities in the game.

Players will ultimately need the Dubious Disk in order to evolve Porygon2 into PorygonZ. Thankfully, both the item and Porygon2 can be found close together when traveling through the Space-Time Distortions. These are rifts players can enter after being introduced to one in the story (as shown above). Although it is possible to find a Porygon-Z inside of these, too, the Dubious Disk and Porygon2 are much more common to spot.

Secondly, the item can actually be bought at the Trading Post in Jubilife Village. Of course, you’ll need to find satchels in order to earn Merit Points first — the only currency trainers can use at this shop. The Trading Post will offer the Dubious Disk for a whooping 1,400 Merit Points; so, you may need to hunt for several satchels before you head there.

Once bought or picked up, simply drag the Dubious Disk from your satchel over to the Porygon2, and you’ll have yourself a brand new Porygon-Z.

Related: Where to find Razor Claw in Pokémon Legends: Arceus