FrankenBiker that's it!
http://www.bumm.de/index-e.html
TOPLIGHT
* with integral large reflector
* With bulb 6V/0,6W
* Tools are not required for bulb changing
* Available with plug or crimp connectors for current and mass
* With approval D and E
EDITED: Do not use this reflector on the back of the helmet.In an accident it could injure your spine. Back to the drawing board, seeking a flatter reflector that shows at the three angles like the one Franken found.