You can see one
here
Most of the fork braze-on tabs not really stiff enough. You are better off fabricating your own.
Note that the location of the dynamo must work with the pivot to increase traction. With vertically oriented pivots you need the roller to be on the trailing side, not the leading side of the tyre.
If you have a horizontal pivot it makes no difference.
I use sidewall and hub dynamos. The hub version is much better, especially for regular and long duration use and in all weathers/conditions. Wheel bearing overhaul with a dynohub is a tricky business.
The sidewall is OK for occasional use because it is drag-free when not in use. The position and stiffness of the mount are critical for performance.