I have an idea, it might not be a good idea but maye you can get something out of it, you should tell him that he should think on getting another girlfriend, tell him that he should move on, grow up to be a good man, and direct him to the pickup community where he could learn a few things about girls and dating and that should help him to overcome it, a nice site would be
Fast Seduction 101: Art of Pick-up and Seduction there is a guide there and community, attention, im not suggesting that you tell him to become a "pickup artist", or a Don Juan, im just saying that it would be good if he could learn a thing or two about himself and dating/relationships.
Good luck.