Ok, I took the air filter assembly apart today, just so I could see what filter element was in there.
The only thing printed on the filter element is "Kymco KKC3".
Cross-referencing this with the Dink 200i parts list gives a part number of 1721A-KKC3-900. The picture in the parts list looks like the filter element in the scooter.
This is exactly the same part number that the Kymco Grandvista 250, the Grand Dink 125, and the Dink 125 uses.
I found the following vendors selling them:
KymcoPartsOnline.com $19.80
MoxieScooters.com $17.99