One of the dilemmas that I was going to have to face going with a handle bar bag was where to mount my headlight because the way most of these lights mount, they are made to sit on the handlebars. The ideal location would be on the non drive side fork blade and I have a light that would work but it's old and unreliable.
My solution was to take an old reflector mount, make a few bends, and attach it to where the fender mounts to the fork. This particular reflector mount also had a hinge so I cut a piece of carbon fiber from a busted seatpost to serve as the light mount and screwed it into the hole on the hinge.
After a test ride, having installed my new handle bar bag the one thing I noticed is that there was a little vibration on the fender so I glued a piece of rubber stripping underneath the bracket where it comes in contact with the fender and problem solved!