I have an Anker powerbank for that, if my phone ever gets low I just plug it in in my bag.
Though it never got this far to be honest, my Galaxy S22 lasts for 2+ days (so charging it in the evening for half an hour is usually enough to never worry about battery).
Bought the powerbank 6 years ago to play Pokemon Go (go figure), but then they removed the steps feature (showing you how far away you are from the Pokemon, leading to people actually hunting them down instead of sitting around in one spot) and I stopped playing (: