Battery with same dimensions and same capacity for the unit can be found here: https://www.aliexpress.com/item/32820495056.html
If your unit stops working and the LED Indicator is flashing alternating green and orange it means that you reach some stupid hardcoded lifetime of unit. Check FAQ on https://acceledent.com/faq/:
Open it, desolder Microchip SPI EEPROM 25LC1024, then use Arduino with this sketch to dump content and then another sketch to clear the whole EEPROM. Solder it back and the unit is again working. My dump is saved here.