BTW, their specs says it wants minimum 100W USB PD, so you'll actually need a different battery that can do that which is probably going to be heavier (the NB20000 tops out at 45W), assuming that's accurate.
The 630g Anker 737 PowerCore 24K might be a good option, and also the 765g HyperJuice 245W.
So this adds 0.3-0.45kg to the estimate.