+1 for batteries from Convoy! I’m a happy customer of @Simon_Mao re: batteries, have purchased a bunch from him and couldn’t be happier. Unfortunately he’s currently not carrying any high-current-drain 18650 batteries: there’s none in his 18650 battery catalog page , and I even contacted him directly and he confirmed he could provide me with none 
BTW, he is currently listing the N41 and for those that have a use for them (I don’t, as it has only 10A max CDR and I need at least 20A), he’s selling them considerably cheaper than even Vapcell itself (at least in 2-piece quantities: $19.33 with free shipping so $19.33 total, vs Vapcell at the link above: $19.12 plus 8.41 shipping so $27.53 total). And as he ships them inside “carrier lights”, they are shipped by air and arrive very very fast (last time I purchased from him they arrived in exactly 19 days, and it was Christimas Season to boot…