The brackets I got with my two-piece one were strips of 0.8mm stainless, 16mm wide. The end of the strip is rounded off, and a hole drilled for the bolt. I replaced the brass bolts with nylon ones as they are less visible. The strips were about 3" long, and get bent (simple 90-degree bend) and trimmed to suit. They drop down between the door metal and the door belt.
In the photo below, my bracket has slipped out (probably because of my fat elbow leaning on the windshield
) and is sitting between the door belt and glass.
Cheers,
Harv