I don't have a lot of experience with Dynamos but agree with Paul that the power put out by a single dynamo is limited. Items like a laptop or DiNotte Daytime Rear light are going to draw humongous amounts of power. Trying to charge them from a Dynamo would be a major ordeal. Even if you incorporated a second dynamo it would be a stretch.

A better option might be to carry a rather good size Li-po battery ( for back-up ) and carry a compact fast-charger along to charge it (when you find a spot to charge it.). You could make a game of it. Find the spot to draw free power "from the man". You got to stop and eat somewhere, might as well be a place that has electrical outlets. This not an idea you should shrug off. More and more I'm seeing electrical outlets for the hybrid cars at certain shopping centers. Li-po batteries can handle a pretty fast charge. I can't guarantee how well it would work but it is an idea worth looking into.

Anyway, incorporate both dynamo and fast-charging back-up battery ideas and you might get something that at least comes close to meeting your needs.