Energy Scavenging with Shoe-Mounted Piezoelectrics
Article on how to generate electrical energy by walking.

Human-powered wearable computing
Article describing the physical limits of generating energy directly by the human.

Making a battery pack adaptor for the M1 HMD
explains with photos how to adapt a model-building battery pack for wearables.

NRG Research
Produce several battery belts and vests (and professional video lighting equipment). Catalogue online.

Energy+Plus
Build and rebuild custom-made battery belts. [Java]