Update Out of Stock but link above still works (thanks commenter)
B&H has the PNY StoreEDGE MacBook SD card adapter 128GB for $64.95 with free shipping. That’s $5 less than our previous mention. These cards are designed to live inside a MacBook Air/Pro or Retina and provide a handy additional 128GB or 64GB of space. The shortened size means they are flush with the sides of the MacBook and won’t protrude out. Rated 4 stars on Amazon.