There's the Manfrotto 700RC2 (0.5kg), approx 40% lighter than the 701, but it does advise "Minimum load of 3 lb (1.36kg) – anything lighter might experience backlash upon stopping a pan movement".
The new Manfrotto 500 is much lighter and has a snappier quick release. It's new so don't know about durability.
The lightest usable video head has to be the Velbon PH-368. But it is all plastic and will surely break if you manhandle it.
The Weifeng WF717 is very good when it's new but tend to break apart over time. Knobs will rattle and plate will start to slip. But because it's so cheap, I keep replacing them.