joe8mofo
Contributor
AliExpress sells the DiveNav's carbon monoxide S+4 2ECO sensor for about $25.
https://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20200611073549&SearchText=2eco
That means that with an ESP32, resistor, and screen one could build one.
Here we go: US $6.91 27% OFF|TTGO T Display ESP32 WiFi E Bluetooth Module Development Board Para Ar duino 1.14 Polegada LCD|Replacement Parts & Accessories| - AliExpress