If you find yourself further than 6ft from an outlet for a long enough time that you're not able to use a laptop, you either A) need to get your house up to date on the electrical code or B) get a smaller house...
That said I've never seen one longer than six feet (seen above) made for the power brick, so I guess if that doesn't work then the other option is to use a regular extension cord, as per GGJ's suggestion.