I'm afraid I can't give you mine, but I can help you evolve yours if you'd like! I don't need anything in return, but if you'd help me evolve my porygon into a porygon2 (I've completed my pokedex but I'm making a living dex ^_^) then that would be really appreciated!
Surely you could get one? Have you completed the main story of the game yet? (You get a kings rock easily by battling the trainer school principal) And Poliwhirls aren't hard to come by, you can catch them in Maile Garden or you could evolve a poliwag, it's up to you! Sorry I couldn't help you out, good luck though! I hope you find it ^_^
The new games don't have a national pokedex, just the Alola one! There are 300 pokemon in the alolan pokedex so it honestly isn't that difficult if you use the GTS and make sure to catch all the ones you run into while you complete the main story. All for the shiny charm, amiright?