I've not yet been able to find one for a 150, but in the past have used this one which has been close enough for my purposes:
http://binatani.com/wp-content/uploads/2013/02/wiring-diagram-Kymco-Super8-125cc-engine.jpgKeep in mind that although the 125 vs 150 engine size may not be an issue from a wiring perspective, these for a non-US version of the scoot, and the US may be different in:
1) The headlights are re-wired to be permanently wired on (so there is no off/on/park headlight switch),
2) The light control box may be wired up differently,
3) The park lamps are disconnected, and
4) The turn signals wiring is rewired/extended to go to the turn signal stalks.
