This is a smaller version of the https://blog.tehybug.com/index.php/2022/02/20/tehybug-senseair-co2-sensor/ its smaller because it uses a different sensor SCD4x which has a smaller size. The new board also has an OLED Display connector, the senseair s8 board was upgraded too and also supports a display connection.
Here is a demonstration video of the new mini board in a 3d printed enclosure. https://youtu.be/aRd_TyuY4yc
I have also released firmware for OLED Display support and HomeAssistant autodiscovery, which is available on GitHub: https://github.com/gumslone/tehybug/tree/master/tehybug_co2_firmware
An enclosure for 3D Printing is available on Thingiverse for download: https://www.thingiverse.com/thing:5494215