@jasonculp listed a lot of good links from a reputable site, VapeNW.com... There are also good deals from other reputable sites, such as VaporDNA.com, 101Vape.com, codevape.com, and Sweet-Vapes.com. Some people have had issues with Sweet-Vapes, but I've not personally had any problems with them for the few orders I've made in their direction.
VaporDNA has the SubTank Mini (top-tank) kit for $50 right now on sale, and 101Vape runs battery sales every 3-4 months, where you can pick up pairs of LG or Samsung batteries for as little as $7. I'll also recommend the i4 or d4 charger from Nitecore... extra charging capacity is good, and you'll eventually need it, lol