Dynamo or genmerator lighting systems are a valid alternative to barry power and can be retro fitted to any bike. You dont have to worry about recharging and they are always on your bike. They are also resistant to thieves.
Hub generators are better for regular use, they are very efficient and never slip, sidewall dynamos are good for occasional use (they are friction free when not in use) but sidewall systems need a good solid mounting system.
Modern European dynamo lamps are specially designed for bicycles and make more effective use of the illumination than generic sealed beam lamps. You get a concentrated rectangle of light with a peripheral start pattern.

Harris and Peter White both sell good systems.