Another option is the Phoenix CE3 from gotvapes. It has the 510 threading, and when filled properly will likely last you the day. Plus, no filler material, and it is clear so you can see how much liquid is left. You will go through a little more liquid, but it is a good alternative to the regular cartomizers. It looks slightly intimidating at first, being clear, but it is slim and about the same diameter as regular cartos, just longer - the same as XL cartos.
What she said.
Also, the Vivi Nova works great on my KGO, especially with the 1.8 or 2.4 ohm head, and holds plenty for all day. But its a lot larger in diameter than the KGO. That combination might be a little funky looking for you. Apparently a new smaller version is soon to be released, but I haven't seen them for sale yet.
Another option is the stardust clearomizers, but they are hit or miss for me. Some work great; some not so much.