sunwayman makes a "L" shaped flashlight called L10A, i think. its not meant to be a headlamp though, so i dont think it comes with headbands and such.
fenix MC10 and MC11 are angled, and swivels. again, not a headlamp so no headband with it.
Rofis has come out with lights that its bezels can also swivel to a 90 degree angle.
spark headlamps, although not an "L" shape. its lights come out the side of the tube.
of the lights i mentioned i only have experience with the fenix mc10, and its not without its flaws...