Crucial Ballistix Sport LT 2400 MHz DDR4 Laptop iMac Memory Kit 8GB (4G x 2) | eBay
OWC 64GB DDR4 2400 MHz SO-DIMM Memory Upgrade Kit
8GB DDR4-2400MHz PC4-19200 SO-DIMM Memory for Apple 21.5" iMac with Retina 4K Display Mid 2020 by NEMIX RAM System Specific Memory - Newegg.com
Amazon.com: OWC 32GB (2 x 16GB) PC19200 DDR4 2400MHz SO-DIMMs Memory Compatible with Mac Mini (Late 2018), 27" and 21.5" iMac (Mid 2017), and Compatible PCs (OWC2400DDR4S32P) : Everything Else