It's possible to build a Raspberry Pi tablet within these screens (5" or 7"):
https://www.raspberrypi.com/products/touch-display-2/
Total cost will be around 130$, too.
1280 x 720 on a 5" would be 293.72 PPI, for the 7" 209.8 PPI.
Edit: or there are some monitors within usb-c, if you can just connect them to a phone:
https://www.aliexpress.us/item/32568...2usa4itemAdapt
(7")
or:
https://www.amazon.com/LESOWN-1024x6.../dp/B0CZ735593
(
https://electronikz.com/products/7in...i-wide-monitor)