Spare Batteries for Feiyu Tech FY G3 or FY G4 gimbals?

I am interested in purchasing a FY G4 3-axis Handheld Gimbal. Just wondering if anyone sells spare batteries for it, as I am heading into a remote area and will need to be filming for a few days without recharging. How long do the batteries last and how much would extras cost?

Although we dont sell any on our site, you can order some specifically for the FY G4 here -">Neewer&reg

Otherwise you can order some generic batteries here -">Genuine

However you can also search online for some 18350 900mah batteries as that is the ones the G4 uses.