Sidorenko Designer Laptop Case Laptop Case Sleeve for 7 inch / 10 - 10.2 / 13 - 13.3 inch / 14 - 14.2 / 15 - 15.6 inches / 17 to 17.3 inch Neoprene Sleeve
looks very stable, and 13 inches will fit very well with the MacBook Air 13.3 :) really stinks pretty as some had already written, but goes by rather quickly.