If you want long run time, an 18650 light is best. You can get around 3500mah. This new Boruit model is my new favorite. It’s very light for an 18650 lamp. Plus it has a lot of great features and is pretty cheap as well.
If you do really have to have something lighter (if that’s your main criteria) maybe check out my attempt to list all the decent head lamps. There are weights for some of them, plus you can see models that use the battery you like. You can then look up the weight.