OWC 4GB PC12800 DDR3L 1600MHz SO-DIMM Memory Compatible with 2011-2015 iMac, 2011-12 Mac Mini, and 2011-2012 MacBook Pro (Non-Retina Display) Models (OWC1600DDR3S4GB) at Amazon.com
Synology RAM DDR4-2666 Non-ECC SO-DIMM 4GB (D4NESO-2666-4G) at Amazon.com