Apple iMac 21.5" All-in-One Desktop Computer Core i5-4570R 2.7GHz 8GB RAM 250GB HDD Mac OS Mojave Late-2013 w/ Keyboard & Mouse
A-Tech 32GB Kit (4x8GB) RAM for Apple iMac (Late 2012, Late 2013, Late 2014, Mid 2015) | DDR3 1600MHz PC3-12800 SODIMM 204-Pin Memory Upgrade at Amazon.com
timetec 32gb kit(4x8gb) compatible for apple ddr3l 1600mhz pc3l-12800 cl11 for imac (mid 2011, late 2012, late 2013, late 2014 retina 5k, mid 2015 retina 5k) sodimm memory module mac ram upgrade - Walmart.com
SOLVED: Need more ram for iMac 21.5 late 2013 - iMac Intel 21.5" EMC 2638 - iFixit
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET