Approached one eink display manufacturer for custom size... lets see.
this is SPI panel, so need a micro inbetween to "convert" i2c to spi, but that is no problem.

Active area with this is about max 52 x 80 mm as there is some frame around it, and to keep it thin, flex cable eats some space close to camera.

Corresponds to a 3.7" diagonal size.

below is quick illustration how it could look.