Hi there! I hope to be of some assistance with your question here today! Social & emotional confidence can be a very challenging thing to manage when one has faced rejection in social situations. This question is very interesting, as there are various levels in which we can approach the problem.
First, has your son ever had a "mentor" or someone whom he looked up to greatly, who exhibited the type of confidence that he wishes to develop? Sometimes, having an example of how to start conversation, how to approach others with an "open" stance physically, (arms uncrossed, smiling, making eye contact, etc...) and then simply mimicking these behaviors can help someone to learn how to do it. "Fake it until you make it" is a good motto; practice actually does work to create an approachable persona.
(Also, tell him that an easy way to start conversation is to ask questions about the person, kind of like interviewing them... people love to talk about themselves!)
As far as the actual logistics of finding potential partners, online dating is a very popular forum for meeting others with similiar interests. It is non-threatening, as you can become familiar with others but only meet if you feel there may be a possible connection. One free website is "PlentyofFish.com" that he might like to try.
He has a choice to make; behave as if he is a victim of circumstance, or take action to keep himself involved in living and being around others in order to meet new people. Action is the antidote to powerlessness & unhappiness; joining organizations that are involved in things he enjoys, getting out and participating in life will give him more possibilities for success than just shutting down and giving up. Encouraging him to stay positive will attract more people to him than will negativity... which only repels people. He is lucky to have your support and care!
I am attaching a link to an article regarding gaining social confidence: http://www.peopleskillsdecoded.com/how-to-gain-confidence/
He might like to read this and see if any of this is helpful to him...
I see that you are offline, and so I will wait for any further questions or your reply; I hope this advice was somewhat helpful to you! Love might just be right around the corner for him and with a few little changes to his thinking and social behavior, the time may be very soon that he finds what he is looking for!! :-)
Hello, Bob... I found one more link with some better info than the first; I hope this gives more helpful advice! http://suite101.com/article/overcoming-social-anxiety-a42176
All the best to you!!