I found an off the shelf external lap battery that will keep the 2.1 powered up for 3hr 45min in combination with the camera's internal battery. The battery came with the correct cable. I have tested and used the smallest version. There are also 2 versions larger.
Check this out at Amazon.com
BatPower EX7H 98Wh Laptop External Battery Power Bank for HP Pavilion Envy Spectre Split Slatebook Chromebook Streambook EliteBook Notebook(Circular Connector) USB QC Fast Charging Tablet Smartphone https://www.amazon.com/dp/B07DGL6DX7/ref=cm_sw_r_other_apa_i_4okLEbKVVQY6D
Check this out at Amazon.com
BatPower EX7H 98Wh Laptop External Battery Power Bank for HP Pavilion Envy Spectre Split Slatebook Chromebook Streambook EliteBook Notebook(Circular Connector) USB QC Fast Charging Tablet Smartphone https://www.amazon.com/dp/B07DGL6DX7/ref=cm_sw_r_other_apa_i_4okLEbKVVQY6D