I have used the red carolina keepers, they also come in clear. They are a great and simple design that I actually like using better than threaded bobber stoppers becasue once you are done with the setup, you can take the keeper off and use it another day. I have been able to mostly find them at Academy for a decent price. They also work great for a pegged texas rig set up, or you can use two of them to have an adjustable drop shot rig.
Keep your lines tight, and your hooks set!