The best I can offer is a Darkrai that someone else got in their save and then uploaded a file containing it. I can use that file make a duplicate of that Pokemon, if that is OK. Trade me anything for it.
This topic usually deals with people asking for Pokemon to be created for them. These are Pokemon that have never been in the "wild" but when I make them, I have a preference for creating them in such a way that if someone had caught the Pokemon in the wild and you were able to compare it to the one I made, there would be no difference.
If there was a rare Shiny Pokemon that you wanted and were OK with trying this. I can create it and trade it. If you were not happy with it you could just release it.
Otherwise I am not sure there would be any traders looking in this topic. You may like to try a trade request in the normal game topic as it is a specific game related request (though I can't recall seeing any trade requests in there). Another alternative is Gamefaqs I suppose as there is a Trade Board there.