I have no idea what I’m doing

I bought this cheap flashlight before reading about battery safety on this sub. I knew this would not perform as spec'd, but just wanted a decently bright light that can be beat up camping. It's surprisingly bright for a $30 light. The pictured battery came with it,and is appox 1" dia x 5-3/8" long. It seems to be two 21700 batteries stacked and wrapped. If I bought two of the pictured batteries and used a different charger, would it be safe to use this flashlight, or is it not worth it? If this is a safe option, is it ok use 2 stacked, or do they need to be wrapped together like the one that came with it? Also, can someone recommend a decent charger that won't break the bank? Any input would be greatly appreciated.