AFAIK, none of the game artists -- for any of the games -- is free or taking commissions. You can go digging and see but I would think most of them are busy making art for the games.
My advice is to take time and look for artists -- Google is a powerful tool and there are more NSFW artists now than ever these days. I, in particular, have one that has been super solid and I found just patrolling DeviantArt. Just apply yourself and you'll find the right artist to pay.
Oh, and that's another thing: bring money. Artists cost money.