Most of the car jump starters will charge a phone many times. They're a bit heavy, though.
That said, I have a Power Bank, 25,800 mAh. Made in China like all the rest. They own the lithium. It's been pretty good and it will also power my heated vest for a long day.
This one (I have sinned and bought it from Amazon):
POWER BANKMy wife has a 10k Lonkuu that works very well for charging phones. I tried to borrow it for a winter camping trip to heat my electric vest and it won't even turn on. For some unknown reason, not all power packs will work with all vests. My jump starter will work great with the vest but it's too dang heavy to carry around while hunting. If you have or are thinking of a heated vest, do some checking with the vest manufacturer to make sure you get a power pack that's compatible.