Kirdan, In one of today's papers someone wrote to an agony aunt with your problem. The answer was sympathy for your position. If you are not someone who enjoys taking the initiative in seeking social contacts, it is difficult. But at the end of the day you can only find new friends by going out to places where you are likely to meet them, and they meet you.
Yes, there are many people out there like you, sitting in their houses waiting for someone to knock on the door and offer to befriend them but, if you all sit inside and wait for people to come to you that is just not going to happen. The only solution is for you to go out into situations where you are likely to meet other people and have the opportunity to meet someone who will become a friend.
The best, no, the only way, to do that is by finding some organisation that reflects your interests and operates on a social basis. This is why Gnetters have suggested groups like the Men's Shed Association, Ramblers Association, University of the Third Age. Other possibilities are doing a voluntary work, a very varied sector. There may be a volunteer opportunity that would benefit, perhaps from your work experience, or other specialist knowledge.
Go online and search for activities going on in your area. Some local authority sites often have a volunteers register. Your local library will have posters about local groups and possibly more information if you ask Quite often groups will advertise with notices in shop windows and on local notice boards.
The ball is in your court. Only you can pick it up and hit it.
