Your best bet would be the Trade section of the forum. I missed out on a few events but about a year or two later I found someone on there who had the Event Legendaries, and they were willing to clone them for me (100% legit, not hacked) so I'm sure you'll find someone willing to help.
Go through their trade threads and see if they still have legendaries available, and send them a PM. I warn you though, occasionally people might try to offer 'mons that appear to be Event mons, but aren't. So check on Bulbapedia and make sure the Pokemon you're recieving has the right name and ID, and that the Pokemon has the Fateful Encounter tag.
Try the quick trade thread too, it might take a while but people may have just what you need.
Hope that helped!
