Waterproof headlamp, double AA with lithium backups.
Aside from big box or discount stores, which sell cheaply made, heavy and unreliable AA headlamps, good quality double AA headlamps over here, are rare. I cannot recall the last
good quality 2xAA headlamp on the market in the last 1/2 dozen years or so.
Big manufacturers here such as Princeton Tec and Black Diamond mainly sell 3xAAA or 4xAA models. There are also some 2xAAA models such as Black Diamond Gizmo but I cannot see the point of having one of these as a comparable 3xAAA lamp only has a slightly bigger battery casing.