Go to P2 labrotory (you need Genesect event) an go inside the lab and a man will give you it
i have a dubious disk i can give it to you send me your F.C and name ok
Cheat code of dubious disk is very long but really great so here it is 94005535 FFCF4232
Mt.Silver
you go to the p2 lab
The Pokemon that uses the Dubious disk is Porygon2 to evolve him into a porygon-Z
route 225
Use the dubious disk to evolve Porygon or Porygon2 to Porygon Z
route 225
It evolves Porygon into Porygonz.
They are the evolutionary items for porygon.
You trade porygon 2 while it's holding Dubious Disk. you can find the Dubious Disk by surfing acrost the larger body of water on route 225, near the survival area.
make it hold dubious disk and trade it ^_^