I use the same approach as Ubehebe. I also buy cells for Fasttech and other reputable vendors when I need special or protected cells.
All the Li-ion cells I have acquired using Ubehebe’s approach been excellent so far. You have to get an OEM pack, like Ubehebe’s example, and measure, measure, measure for a bit just to make sure you have solid cells. There was an excellent discussion and testing in a thread that Ohaya started. Here is a link to that thread and a subsequent one.
I have had terrible luck though trying to get 4/3F Ni-mh cells this way though.