I'm solely a consumer of bass pro, not an employee or affiliate in any way.

I have used:
$9.99 38-612-962-11 NO-BATTERY SHAKE FLASHLIGHT 7-1/2''
From www.basspro.com for several years. It has a capacitor and a single LED with reflective mirror. It's made out of ABS plastic.

About 2 minutes of shaking is good for 30 minutes of use. Durable, sufficient light for emergencies. I like it though I keep a real d cell batt flashlight too. It's definitely nice for redundancy though. I was surprised most by how long the light lasts on a minor amount of shaking.