Almost year ago I bought Electrolux PUREi9. Now they multiplicated. (It had some early software issues but now I'm really happy with it) : r/homeautomation
Electrolux Pure i9 products - BatteryUpgrade
7.2V 3.4Ah Li-ion OSBP72LI25 Battery for Electrolux Pure i9 Vacuum Cleaner
Battery Pack Electrolux PUREi9
2000mah Electrolux Osbp72li25 Battery For 900277484 Pi91-5sgm 900277264 Pure I9 900277252 Erv7200db Erv5210iw Rx9-2-4stn 9002772 - Rechargeable Batteries - AliExpress