You can get 128X64 OLED on AliExpress for 3$. Mine draws 2.2mA to show 6 letters, 3mA for 12 letters.
It can be controlled with e.g. ATTINY85 (1$) which can e.g. set the text/image to display and go into deep sleep in beetween sreen updates where it draws almost nothing (< 0.01mA).
2800mAh battery featured in this video will last this setup for more than a month of continuous operation. If you turn the display off e.g. when the lights are off it can last several months.
It can be controlled with e.g. ATTINY85 (1$) which can e.g. set the text/image to display and go into deep sleep in beetween sreen updates where it draws almost nothing (< 0.01mA).
2800mAh battery featured in this video will last this setup for more than a month of continuous operation. If you turn the display off e.g. when the lights are off it can last several months.