I solved this with a ~$200 driver board from AliExpress. I love the result because it's thinner than any other monitor that I own and I can swap between my MacBook Pro and my desktop machine (running either Windows or Linux).
Obviously this requires a little bit of tinkering and the end result isn't nicely packaged like a factory Apple product would be, but it only took about half an hour to put together and I haven't had any issues with the driver board yet. And it was way cheaper than a "Retina" display from Apple or LG.
I didn't bother to mess around with mounting, I just used command strips to attach the driver board to the back of the monitor and mounted the monitor on one of these clamp-type stands:
I solved it by not updating the OS or apps. I stopped updating at Mountain Lion. My older iMac is my scanning and photo editing Mac. A flatbed scanner is permanently attached and Photos from Mountain Lion is still useable. In fact the retouch tool is actually faster (Photos experienced a serious performance regression for the retouch tool soon after Mountain Lion).
Obviously this requires a little bit of tinkering and the end result isn't nicely packaged like a factory Apple product would be, but it only took about half an hour to put together and I haven't had any issues with the driver board yet. And it was way cheaper than a "Retina" display from Apple or LG.