Unfortunately, the only version of the tablet that can be bought directly from Google is the 32GB black tablet. It's available for the price of $599 and if you buy it now, it will ship out on December 19. Hopefully we will see the larger 64GB version go on sale in the near future, along with some different colors as well. Be sure to check out our review of the Wi-Fi only version of the Nexus 9 if you are interested in getting the tablet with the additional LTE wireless support.
Source: Google Play Store