A fellow on the Randon List makes these mounts for $13 + shipping. They can be used to mount a light to the left side of your QR or to a fork braze-on. If you are interested PM me and I'll provide his email.
I made my own mid-fork braze-on mounts - there are details on my
blog here. I used 1" wood doweling so it was almost free, but not as nice as the metal mount above or the Nitto mount someone spoke of earlier. BTW - the Nitto mounts are back in production and available as well [pics below] for a little over $30.
Lamp Holder 3
Lamp Holder 5
Very nice.
If you had access to a mill or something, you could probably make a very light stud out of hollowed aluminum instead of a wooden dowl. The wood will suffice I'm sure, but the aluminum might work better over time.