OWC has announced that it is now shipping 1TB solid-state drive upgrades for the first-generation MacBook Pro with Retina display. The Aura 6G SSD actually comes in a bit smaller than 1TB at 960GB, and has peak transfer rates of 555/530 MB/s.
You can get the 1TB Aura SSD from OWC for $549. However, OWC is also offering to bundle the Aura with its Envoy external enclosure. The Envoy lets you take the internal SSD that's being removed from your MacBook and repurpose it as an external drive. The 1TB Aura and Envoy bundle costs $599. Both the drive and the bundle are available for purchase now.