You can buy a voltage booster that will give you 12v to an accessory while keeping the 6v system. They are usually cheaper than a conversion. They don't work on a high watt stereo though so if you want people to hear you blocks away they won't work.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.