That's a toughy as scooter alternators aren't designed with much extra power. An over wattage
bulb or HID will need more juice. You might look for a whiter bulb, the ones that say 85 watts
from a 65 watt draw. They look brighter, The only problem is the good ones (like PAIA) cost a lot
and don't last long on a motorcycle (or scooter) in my experience as their spec'ed at 13V and the bike
runs at 14V...