The Up-grade evolution item is a difficult one to obtain in Pokémon Brilliant Diamond and Shining Pearl. You’ll need to go through several hoops to obtain it, but once you do, you’ll be able to use it to evolve Porygon into Porygon-2. Here’s what you need to do to find Up-Grade in Pokémon Brilliant Diamond and Shining Pearl.
You’ll have to complete the entire Sinnoh PokéDex. First, you’ll need to encounter all of the Pokémon in the Sinnoh region at least once. After you’ve done that, you’ll then need to return to Eterna City, which you can find between Routes 211 and 205. When you reach this location, having encountered all of the Sinnoh Pokémon, go to the home at the very south, to the left of the city’s Gym. Instead, you’ll be able to encounter Professor Oak you provides you with the Up-Grade item.
You won’t be able to find this item exploring any of the paths, and you won’t be able to find it before this point. That means you’ll need to continue through the Pokémon Brilliant Diamond and Shining Pearl game, collect the Gym Badges and then return to this area. It might take you a long time to reach this point, but it’s a guaranteed method to obtain it.
