I can get you a Ditto if you can get another Porygon. I know they're a bi-yatch to catch at the high levels in Giant Chasm; took me three tries to get one for someone else once. I understand wanting to get help with it.
If you can't get a second Porygon, tis fine; I can deal with that. Anything else not native to B/W you can offer? (White Forest counts since they're exclusive to that and brought by various NPCs.)
We could also do something different if you want; Porygon can breed with Ditto, so I could trade the Ditto for something breedable, we both do breeding, and I trade the new parent back for the baby Porygon. Or something. :D