Up-Grade can be obtained from Professor Oak.
Steps :
After beating the elite 4 and upgrading pokedex to national, go to Pal Park and talk to Professor Oak.
After that, go to the house which is at the bottom of Eternal city.
Go into the house and talk to Professor Oak again. He will give you Up-Grade.
Dubious Disk can be found while surfing.
Steps :
Go to Route 225 near the house by the lake.
Surf across the lake and you will find it.
How to get Porygon : Go to the Pokemon Mansion which is below Hearthome City. Save before talking to Mr. Backlot. Talk to him. If he say something about Porygon in trophy garden, go to trophy garden and catch Porygon, it's rare. If not, reset the game and talk to Mr. Backlot until he say that Porygon is in trophy garden.
Extra Information : You can envolve Porygon by trading 2 times. First time is to trade while holding Up-Grade. It will envolve into Porygon2. Second time is to trade it while holding Dubious Disk. It will envolve into Porygon-Z.