You can already by a 13 inch mobile e-ink monitor.
There's the Onyx Boox Max series starting with the Max2 (the current model is the Max Lumi) with HDMI in
and the Dasung Paperlike monitor.
They are pricey, however.
If you have some kind of overlay screen you can have both worlds. But I was still under the impression that E-ink was the only option. Today I learnt about transflective screens. I hope they catch on. I would buy it.
It can be used as a PC display, which I'd kill for (figuratively) as long as it's affordable. If it's $200 or more, that's not what I consider affordable.
Since such a screen would be most usable outdoors, I wonder about the setup. I guess if it'd be light and thin enough it could be put on top of the screen in that case? Or would you have a separate stand for it?
I have one and use it outside regularly (e.g. [0]), it's pretty amazing!
There's some open-source tooling[1] for it which can control screen features like brightness/refreshes/rendering modes/... and I've set it up[2] to work with my unprivileged user so that I can bind these features to keys in my Emacs.
With these screens you want to use light themes, and use tooling to improve contrast on websites (a friend wrote a Firefox extension[3] which is amazing for this).