The person may not be as desperate as you think. Try to ask him whether he has attended the same event or other similar events in the past and got to know some other people in the room. Try a direct question: "Is there someone here who you think you could introduce me to?" Then you can ask him to introduce you or try to approach the recommended person yourself.
If the common goal is to meet new people at the event, you can join your forces. Agree to approach other participants together. Try to ask a question such as: "I was planning to introduce myself to the group of people next to us and talk to them. Do you want to join me?"
Thank the person for an interesting conversation then tell him that now you are going to move to someone else. Do not worry that it will appear to be rude. Explain briefly that your goal for the evening is to improve your networking skills. Say for example: "My goal is to get to know at least three new people at each event." This way, you will show that you do not think the person is bothering you, you just want to improve your networking.
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Article source Harvard Business Review - flagship magazine of Harvard Business School