LTT just did a video[1] on an 25inch E-Ink display[2] that runs at 15Hz.

It worked way better than I thought it would and is a pretty decent size.

Little pricey.

[1] https://www.youtube.com/watch?v=-ZXrJRpA0Jw

[2] https://www.amazon.com/DASUNG-Paper-Monitor-Knight-Version/d...

The one display I got takes about 2 seconds to cycle. You can make it shorter with partial redraws, but for my purposes, the cycle was the right thing to do.