I can't recommend where to get the carts for a 510, but this is definitely the place to be to find a vendor that will hook you up with a bulk deal. Make a new post kinda announcing you are looking to
buy some cigs and carts, a large order, and see who bites! I still think the 808's would be better because then you wouldn't have to worry about atomizers and have to charge the
batteries less often, but a lot of people swear by the 510's. I have one coming to me now, actually, so I'll see if they live up to the hype.