The only statue that I could find that represents Buddha with shaved head is Tuyet Son Statue, from 18th century Vietnam, where Buddha is represented sitting/ relaxing.
As for the hairstyle on other statues, it is not Greek, but Indian in origin. It is usually called the rishi knot, the knot that sages make of their hair. Shiva is represented with such hairstyle, as are the Hindu rishis, such as Vyasa. A lot of sadhus tie their hair like that, as do Sikhs.