Those scooters are rated for 2 people, 150 kg max.
Carrying an extra battery isn't really an option. An extra battery pack does cost a sizeable portion of the vehicle's net price, quite bulky and heavy (i.e., probably not transportable on the scooter), and usually not easily removeable / replaceable (with some noteable exceptions - InnoScooter has an easily replaceable battery pack IIRC).
But there are other scooters around with much higher ranges... the German Wikipedia actually has a list of available electric scooters, including prices, speeds and ranges http://de.wikipedia.org/wiki/Liste_der_Elektromotorroller). Unfortunately there doesn't seem to be an English counterpart to that list, but I think the German one can give you a good starting point since several manufacturers ship internationally.