Apple 21.5" Certified Refurbished iMac 4K Intel Core i5 2.3GHz 8GB Memory 256GB SSD (2017) MHK03LL/A - Best Buy
The New 2017 iMac: Notes & Tidbits on RAM - The Mac Observer
Apple iMac 21.5" - 8GB RAM - MASSIVE 1TB - macOS X - UPGRADED - WARRANTY | eBay
Used 2017 Apple iMac 21.5" Core i5 3.40GHz 8GB RAM 1TB + 32GB Fusion MNE02LL/A - Walmart.com
Install memory in an iMac - Apple Support
Apple iMac 21.5" - QUAD CORE - 8GB RAM - 2TB - THUNDERBOLT - macOS High Sierra | eBay
Teardown of new 21.5-inch iMac surprisingly reveals user-upgradable RAM, modular CPU - 9to5Mac
Apple 21.5" Certified Refurbished iMac Desktop Intel Core i5 2.3GHz 8GB Memory 1TB HDD (2017) Silver MMQA2LL/A - Best Buy
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