I'm going to suggest this as a starting point: https://www.amazon.com/Waveshare-7-5inch-Two-Color-Interface-Consumption/dp/B075R69T93/ref=sr_1_18?crid=157W7IWJ

I'm going to suggest this as a starting point: https://www.amazon.com/Waveshare-7-5inch-Two-Color-Interface-Consumption/dp/B075R69T93/ref=sr_1_18?crid=157W7IWJZ6EPR&keywords=e-ink+monitor&qid=1708014428&sprefix=e-ink+monitor%2Caps%2C230&sr=8-18 https://www.amazon.com/Waveshare-7-5inch-Two-Color-Interface... It's not a tablet, but it could be connected to a Raspberry Pi. I'd also suggest an ordinary laptop with the display set to grayscale, BUT... the script I was using to put my laptop in grayscale isn't working anymore. and I don't know why. That's probably something I should follow up on. (My computer is using picom with the glx backend as its compositor. Anyway, before, I could just switch everything to grayscale if I wanted. I found out it wasn't working two weeks ago but I've been too busy to find a fix).