Argentine leather case maker Vaja has released Retro, a new series of stitched-stripe cases for iPods, iPhones, and the MacBook Air. The cases start at $39 and include: Retro Slim Bag for iPhone ($39, shown): A sleeve-like case with an open top. An alternate version called Retro Slim Jacket for the MacBook Air sells for $180, and closes like an envelope to protect the computer. Retro Dockable for iPhone ($75): A flip-style case with a bottom design…