Simply attach a headlamp to the strap and quickly remove it. The pocket clip can stay on the light.
This is an experimental design and although I had run a FEM on it I'm absolutely no FEM expert. The included design is for a Sofirn SP40 (or similar lights with more or less 22 mm diameter). You can modify the design using FreeCAD 0.19+.
The printed clip is riveted to a piece of leather. A big light like the SP40 is too heavy to use without a top strap.