Chris P's suggested products are first rate, but i can't help but think that similar weight reduction could be found using an Claricord elastic neck strap, which will give the instrument complete freedom to move, it will just feel lighter, connected to a ring mount from Stephen Fox similar to the one sold with the ERGOBrass product Chris linked.
Of course for those with neck pain, Chris' options may be best, supporting the instrument from below rather than this, which supports the instrument from the neck above.