OWC 16GB (2x8GB) ram Upgrade PC3-12800 DDR3L 1600MHz sodimm 204 Pin CL11 Memory Upgrade Kit Compatible with Late iMac, Mac Mini, and MacBook Pro Computer at Amazon.com
8GB RAM Upgrade for 2011 MacBook Pro & Mac Mini Core i5 & i7 – $34 | OSXDaily
It is Possible to Upgrade the RAM and Storage of Your M1 Mac After Purchase
M1 Mac RAM and storage can be upgraded after purchase, but it's not easy - 9to5Mac
How to Upgrade RAM on MacBook Pro, iMac & More | AVG