Yes with one splice i suspect, but heat in Headlight, current draw etc mean it's probably not a good idea - a low wattage aux lamp is a much better idea if you want more light IMO......
Thinking about it does your bike have 2 separate lights - 1 high beam, 1 low?
someone did this on my old 310 and it melted the connector from the generator.
I suspect if you took your power from the high beam to power the low at the sametime, it would also put the high beam on when you switched back to low beam. some form of relay would be required I suspect.
plus 1 for Aux CREE led lights. plenty of light for low amps,
2 relays and a diode with a decent sized wire fused feed from the battery. How many watts is the alternator?
That's what I did on the Cyclops headlight I have on my DRZ.
Most bikes (and older cars) have long wire runs to the headlight bulbs which give too much voltage drop and thus doesn't run the bulb at full brightness. Putting a small relay on there and feeding that with thicker wire will brighten up the head noticeably. Then as Nige said, once you have relats you can link across with a diode to both only together.
Check you have 55 watts of spare output from your stator before doing this or your battery will not charge.
Don't do this with H4 bulbs btw as it'll over heat them, the glass turns black and then the bulb fails.