To put things in perspective I paid £325 for my chair, so this headrest is almost half the price of a refurbished chair. Or to put it another way, you can buy a reasonably good no brand chair with a headrest for similar money! BUT if you have a Herman Miller Aeron chair and you want a headrest, you really don’t have much alternative.

https://www.amazon.com/Engineered-Now-Headrest-Classic-Herman/dp/B01BZC8ELI