The Nexus 6? Yeah, so popular was the device when it first came out in December last year that it sold out straight away, leaving everyone else crying into their perfectly functional but nonetheless outdated Nexus 5s. Now, almost two months later, Google Play once again has stock for most models, with you want to grab it from the source.
As Ausdroid's Chris Rowland points out, if you hit up the Nexus 6's product page on Google Play, you'll see that the Midnight Blue model has stock for both the 32GB ($869) and 64GB ($929) versions, while the white is only available with 32GB.
A little info box mentions that JB Hi-Fi also has units, if you don't mind dropping by your local store.