If it's a standard Provari, it will use 18490/18500 batteries. I was hesitant about them, thinking I would prefer the extended cap and bigger batteries, but the 18490 batteries last all day and make the unit a nice size.
Provari recommends AW IMR batteries, and they sell them on their website. RTD Vapor also sells them, maybe a little cheaper. They are a well-respected vendor here. They also sell chargers. You might do a little research on the chargers here. I have a Nitecore 4 that has worked well for me, but there are several highly recommended chargers to choose from.