fasttech has always been good for me, theres other sites but the prices cant compete. When they can compete with prices, they get you with shipping (like gearbest). fasttech stock is ginormous also, biggest selection of ecig-related gear.
fasttech has always been cheap for me and every order has come through smooth. Just make sure you get the expedited shipping instead of the base free shipping. Most of the time the upgrade to expedited shipping is like 1-2$ only, if your order is big enough the expedited upgraded shipping is free sometimes as well. (just dont use the b ase free snailmail shipping otherwise youre waiting 1month+ for your order to come in, compared to the 1-2weeks for the expedited).