Can you recommend a fixed LED headlight for a bike with a hub dynamo? I have a Batavus Dutch bike for local commuting with a Shimano DH-2R30E 6 volt, 2.4 watt hub dynamo driving a halogen bulb headlight. The light provided is not very bright and I would like to know if I can replace it with an LED headlight for a reasonable cost. If so, what would you recommend?

I should also mention that I would like to bolt the light to the bike in place of the existing light, rather that fix it the the handlebar and unclip it when I leave the bike. One of the major benefits of the Dutch bike concept is that everything is fitted including locks and lights, so it is quick to use for short local journeys.

Given that I will leave the light on the bike unattended, the light shouldn't look too special, and a reasonable cost would be less that $100/£80.
Peter White has done a lot of testing of dynamo headlights and has even put together comparisons of luminance.  I have the Schmidt Edelux and love it.