For those of you that care about stupid light headlamps, that admittedly don’t put out a ton of light, let me tell you about the Petzl e+lite. It weighs 28 grams, which (I think) is about an ounce. It will give you enough light to pick your way down a trail. It blinks. It does bluish white (y’know, 5mm leds) and red. The old model has a whistle built into the strap. It’s really tiny. One of the downsides is that it uses cr2032 batteries. Petzl blather here: http://www.petzl.com/en/outdoor/headlamps/super-compact/elite
I’d position this as a backup light, or something that will fulfill two items (light/whistle) on a required equipment list for an adventure race.
The new model is a bit cooler, in that it has the string band that’s used in the zipka models (although it doesn’t have a whistle).
But, the old one was on closeout at an REI store on the weekend: just over 20 bucks. Maybe yours has one too. I don’t think they’ve got this on the web, so not only is this US, it’s ‘US with an REI store nearby’. (Sorry.)