If you've got the standard 18650 version, I'd lean toward the Molicel P26A—solid 25A continuous discharge, 2600mAh capacity, and it stays fairly cool during use. Samsung 30Q is another solid pick if you want longer battery life between charges. Buy from somewhere like 18650 Battery Store or an authorized retailer since counterfeits are a real problem. Just make sure whatever you grab has a proper continuous discharge rating; that's what keeps things safe in a device like yours.