Check out the Serfas E-Lume 1100 or 1500. Well made, dual LEDs, single button on top. They come with a handlebar or tube mount, but Serfas also offers the S-Unihelmet mount. Not sure whether it offers the adjustments you want.

Serfas lights use a slide in/out mount with a springy retaining clip, similar to a camera flash hotshoe. My older Serfas light has been secure on the bike. Seems like it could be adapted to a helmet.

My method for adapting a light to my helmet is to nestle the light into a vent, then scoot it forward and backward until it's aiming where I want with my head in a natural position. Usually I keep it aimed slightly downward to avoid blinding other cyclists and pedestrians on the MUP. When I need more light ahead I just tip my head up a bit. Works perfectly when I want to give an errant driver the stinkeye. I just look at them and the brightest part of the light is on them -- seems to get their attention.

My lower power helmet light comes with a simple rubber band strap, but it's only 300 lumens (nominal, actually not that bright). For other lights I'd just rig up a homemade velcro strap and elastic bands.