From time to time there have been such contests. SeeU currently has a contest, in the past Sonika has had two contests where you could win a copy of her software or another Zero-G Vocaloid (Prima and Tonio). These contest occur from time to time, so keep an eye out. However, be aware that the chances of you winning a Vocaloid from the language you do not speak is harder, particularly the Japanese branch of Vocaloids. This is because the fan base is much larger and not being able to speak Japanese puts you at a serious disadvantage.