If you don't need a headlamp, there are lots of USB rechargeable lights designed for bicyclists that might fit your needs.
For example, I sometimes use a Cygo‑Lite ExpiliOn as a handheld flashlight for trail runs at night.
I'm not sure what your total power needs are, but they do make small flashlights with integrated solar panels (the ones I've seen tend to be task lights, not bright beasts like your EOS). Still, they might serve to help simplify your system.
(Apologies for the lazy links.)