Does anyone know where I could buy one?

Basically a stationary bike which I pedal, and the motion is converted into electricity at the right specifications to be sold back into the grid. I'm interested in how profitable this could be. If I could make some money per hour etc., comparing it to an actual job.

http://www.los-gatos.ca.us/davidbu/pedgen.html

this guy built various cycle generators. On average for 30 mins output 100-200 watts depending on your fitness.

In all its not worth it in monetary terms as an hours hard riding will get you only a few pence,if that, worth of electricity.