Front light bracket too small. Help!

Hi,

I got a Trek 5900 in Spring this year to replace my trusty Trek 7000
mountain bike. Before I set off for work today I grabbed the light and
bracket from my Mountain bike but when I got to work i've since learned
that the handlebar on the road bike is too thick to attach the fitting.
Therefore I need a new front light ASAP. Any recommendations on a light
which will fit to my handlebars (standard bontrager which came with the
bike)? I don't need a rechargable system as my main riding is on a
morning so it's only a 5 mile ride home on a night via well lit roads.

Thanks.

Dene