Peace!
I wasnt sure if you meant -just- Gen 2 pokemon for the Kantonian forms, but I feel like Johto and Kanto are to close for the Gen 2 to have a form in Kanto.
With that being said, a Pokemon I feel like would have an interesting Kantonian form comes from Gen 5 the Unova region and that is the Dwebble evolutionary line!
(I may be reaching with this idea but I feel you could make it work design wise)
Kantonian Dwebble ( Grass / Rock ) Ability: Dry Skin
So a few Dwebble end up in Kanto through being captured then released, black market processing, game corner prizes, etc. These few dwebble in the wild of course mate, they end up being problematic in certain enviroments and there arent any desert or really dry places in Kanto for them to live naturally. Eventually, they come upon Mt. Moon and discover the underground tunnels where the Paras and Parasect mainly thrive. True enough, its a bit more moist than the Dwebble prefer, however Mt. Moons underground tunnels end up being the safest and most comfortable place for the Dwebble to live.
Living alongside the Paras and eating upon the parasitic mushrooms that abundantly grow from Paras's spores, the dwebble undergo a transformation. Since their bodily constitution is much like the Paras, the parasitic spores begin to overtake the Dwebble community as they have the Paras and Parasect. These parasite infected Dwebble no longer find Deserts and warmer climates more suitable, and being migrating out of the cave in order to spread their spores. Spores try to grow on Dwebbles back, but the Dwebble resist and pick them off early because it makes them uncomfortable while in their Rock. Eventually, a symbiotic relationship forms between the parasitic spores and the Dwebble. To allow the spores grow, and maintain their shell like comfort, the dwebble begin cutting petrified wood instead of pure rock so the spores will have a place to grow healthily instead of on Dwebbles back directly. This symbiotic relationship gives Dwebble the Grass typing and access to moves like Spore, Leech Life, Leech Seed, Strength Sap, Aromatherapy, Giga Drain, and Growth! Also, because of the need of moisture to help the Spores, like the Paras, Kantonian Dwebble has the Dry Skin ability.
I know that was long, I apprciate you for reading it. I hope you find it to be a good idea and can work with it! Looking forawrd to seeing what you'll create