This requires work on you part.
You need to cultivate a large circle of associates through Linked In.
First you complete a profile, then join up forums which concern your field. Try to respond to posts and try to post something every few days, even if it's just a link to an interesting article in your field. If others respond to it then you can try adding them as friends on Linked In.
Being their friend will help you because professional head hunters who specialize in your field will be able to locate you once you have many friends who are also their friend.
If you do this consistently pretty soon you'll have a few hundred friends and the phone won't stop ringing.