@Rremolo
Hey, you can also try to Headbutt trees in the starter town in Johto. There's a small chance to find Cyndaquil everyday there. You just need the first and second Johto Badges to be able to teach Headbutt and use it there and a pokemon with 150+ happiness that can use the move.
You can otherwise hunt it in the Johto Safari Mountain Zone. You should be able to access it after 5 badges in Johto (as far as I know) and you should be able to find many Cyndaquil with enough patience.