Type-C Aluminum Monitor Stand Hub for iMac - Satechi
Amazon.com: Hagibis iMac Hub with 1000Mbps RJ45, USB C 3.1, USB 3.0 Ports and SD/Micro SD Card Reader, USB-C Clamp Hub USB C Docking Station for 2021 iMac 24 inch (with RJ45) :
increasing USB ports on iMac late 2012? | MacRumors Forums
iMac (27-inch, Late 2012) - Technical Specifications
Aluminum Alloy USB 3.0 Hub Type-C Adapter Splitter with SD/TF Card Reader Clip-type for iMac 21.5 27 PRO Slim Unibody Computer - AliExpress
Apple iMac 21.5-inch (December 2012) review: The smaller iMac Windows PCs can pick on - CNET
Add USB-C ports to an old 2014 iMac - Ask Different
Review: 21.5-inch 2012 iMac takes two steps forward, one step back | Ars Technica