The Streamlight Argo HP can be had for a little over $30, and is "professional grade". It includes a rubber strap for helmet attachment. I got mine at the local fire/police supply store, but they are available online too. It comes with two Duracell Ultra CR123's, but I only run mine from a single 17670 Li-Ion, with almost no detectable drop in brightness. Low-Hi-off operation from the top mount, light-touch button. Figure about 20 hours on low, which is none too dim, and about six+ hours on high. It's beam is a fairly classic hotspot, with excellent throw, surrounded by a wide spill. They now use a Cree XRE LED, where the older ones used a side emitter Luxeon.
It is a lot lower cost than the "premium" lights, but a lot better quality than the cheapest ones out there. Good luck.