Drag Specialties headlight brackets - Chrome or Black
These are pretty cheap, but actually worked pretty well. I ran them for a long time with no problems, though the bolt and nut rusted a bit. The 38mm clamps fit the 38mm forks ok, I think I had to bend them open a bit to get them to fit right, but that wasn't too hard. The headlight I used was just barely able to fit without the can hitting the frame. If these brackets were just a little bit longer, they would have been even better.
Here they are in Chrome:

Here they are in black (I stripped and painted the chrome ones I had):

Fly Racing headlight bracket - Chrome
I bought this bracket because I wanted a longer bracket than the above set in order to make more room for the headlight can, and have more room for routing the brake lines, throttle cable, and electrical lines. They worked fine, though IIRC they were a bit small. I had to use extra long bolts in order to make the 38mm set fit my 38mm fork tubes. Other than that, they were fine. They are a bit longer than the drag specialties set
Here they are on my XJ
Homemade: How it was done
Here is what I run now. I had trouble finding any to fit the 54mm R1 fork tubes, so I just made my own using some hydraulic pipe clamps and steel strips I welded together and painted myself. I love the simple look of these. I put heat shrink around the clamp to make them black figuring this would last better than paint.