Since there's currently no 6IV Ditto giveaway on this site, you're better off catching Dittos with Perfect IVs through S.O.S Battles, though you pretty much have to grind your way to get at least a
4-5 IV Ditto, by doing over 40 Battles. I'll provide a link on a guide on how to do this:
https://www.reddit.com/r/pokemon/comments/5eahum/how_to_chain_for_iv_dittos/