I’m not sure about the electrical load that a vibrator pulls, but there are small bike dynamos meant to power headlights that you can use while riding — they might be able to provide the charge for a small battery vibe, or a more reliable solution that would work for the wahl or another plugin could be to buy or find a golf cart/car battery, charge it up and put it on a bike carrier-rack, hook it up to a DC-AC inverter to use the vibe and then charge the battery back at camp or find someone with a charging apparatus (solar, a bike generator, windmill, an RV, whatever). The latter is a lot like the sound systems at critical mass, though heavy it is fairly portable and easy to do.

Another wonderful thing is since the bike generator is also a DC motor one could probably figure out a way to convert from a generator to a hardcore vibrator. So one minute you could be charging a battery, the next you attach a weight to the motor and change the circuit and the motor is turning (and vibrating something).

Funny enough, with way too much free time on my vacation (and a reminder seeing the pedal-powered bicycle music festival) I had it in me to get most of the parts together to build a bike generator — although sadly i’m still waiting on a part from amazon and I need to get a bike trainer to mount the thing (and I don’t know if i will be able to craigslist one before burningman).

Let me know if you need any advice or ideas, I’m a bit out of practice with electronics but I have my moments and can usually have some clever ideas on how to hack things together