The 12-inch MacBook introduced in 2015 is now considered 'vintage' by Apple - 9to5Mac
Discontinued 12-inch MacBook gone without a true upgrade - 9to5Mac
Amazon.com: Funut Compatible with MacBook Retina 12 inch Case A1534, Hard Plastic & TPU Protective Case with Kickstand Shock Proof Matt Case Cover for A1534 MacBook 12" with Retina Display (# Gray) :
12-inch MacBook (2015) review: Lighter than Air, but at a cost