Unfortunately, no, there isn't.
The only way to obtain Pokemon from previous generations is to catch them in Sun/Moon, if they're available, or by using Pokebank, which will be released in January. However, Pokebank is only useful for transferring Pokemon from other Pokemon games of previous generations. For example, if you had a Rampardos in your X/Y game, you could use Pokebank to transfer it to your Sun/Moon game. So as of now, Island Scan is your best bet, until Pokebank is released, then you could probably trade others for the Pokemon you want.