Take your Xiegu G90 outdoors and enjoy the field operations.
Your radio will work with different battery capacities and chemistry types, but for size, weight and durability I recommend Rechargeable 12V 6Ah Lithium Iron Phosphate (LiFePo4).
WARNING: nothing in this cable stops you from damaging your radio by connecting it to a wrong voltage battery or with wrong polarity. Red wire goes on the positive terminal of the 12V battery, black wire goes on the negative terminal. Pay attention and talk to a friendly elmer if you are not 100% confident!