A quick look on Amazon came up with this: https://www.amazon.com/Renogy-72000mA...r=8-19&th=1
If you already have some of the new DeWalt 20v tools, (as well as several batteries sitting idle while you're flying) this attaches to the batteries you already have, and has a 12vdc power tap on the side. https://www.amazon.com/dcb091/s?k=dcb091 Make sure you get the DCB 091, that's the one for the heated cloting. The DCB090 looks similar but doesn't have the 12vdc power outlet.
I would imagine the other power tool companies would have something similar, as well as clones of these products.