I remembered this thread after noticing on fenix-store.com that the HL10 (edit: wrote HL05 by mistake) is back in stock:

https://www.fenix-store.com/fenix-hl10-led-flashlight-2016/

33g, 1aaa powered, 3 levels (4/30/70 lumens), waterproof, detaches from headband for use as a right angle flashlight, very nice for this purpose except bloody expensive ($27) for an emergency kit light. Battery runtime on the low level is probably enormous. No idea about parasitic drain. I don't feel likely to buy one because of the cost.

Maybe rather than scouring the rather thin headlamp selection out there, it could be better to invent some kind of headstrap that allows more stable and useful head mounting of a conventional tube-shaped 1aaa light or the Photon light. I'm imagining a traditional 2-piece headlamp strap with a top strap, plus some kind of holder or mount at the very top where you would put your small light. The strap part would be thin and lightweight. I guess this could be tested with some bits of elastic strap and some 3d printing.

Another idea: a periscope mirror accessory that slips over the front of a 1aaa light to turn it into a right angle light, then easy to put into a headband. Or the mirror could be built into the headband.

I still have that aliexpress 1aa light but never did any more testing with it. Maybe someday.