I think there is a solution for you: Power Statistics - #16 by fralb5
Just to nictpic, increasing capacity would mean increasing either physical battery size or energy density - but in any case modifying the battery. External batteries and powerbanks would do the same and are already available 
Decreasing consumption of energy is what you’re looking for… but for such a goal (about double), you yourself might need to stop streaming that 24h yuletime fire from youtube (or other such energy hog [sorry, couldn’t find non-youtube example, but that probalbly makes it more apt here]). Or other drastic changes in user behavior. Mere system efficiency improvements might not be enough.
Pardon my fun but your ask is not a small one and Santa is already finishing up the delivery of last minute Xmas miracles - so, you are very likely to be disappointed.
That being said, the development of better batteries would be an interesting option to solve the problem and something not yet considered in other threads (if my memory serves), where there are more in depth conversations regarding L5 energy.
Does anyone know if the batteries L5 has are actually good or could they be better?