Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Yes but the part is proprietary and basically only comes from being pulled out of another rMBP. They're also very expensive.

iFixit does sell them and you might be able to find one on eBay. Definitely only recommended if you need one for a repair vs to expand your storage.

Look into USB 3.0 external drive if you need more storage. Very fast transfer rate and with an SSD in the enclosure you won't lose to much performance.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.