KoS, I used to have a clip from a wallymart cheap mechanical pencil but, I changed it for a piece of automotive vaccum hose; I think it was 1/4" (7mm) I.D. I'd rather have this since the friction it produces to hold onto the sheath's elastic loop also helps me holding or twisting the extender without the need of removing the clip from the extender when I used it as a stand-alone tool. I've had the hose (and the extender) for 1 1/2 years without ever "misplacing" or loosing it.
Here's a picture of the extender; Hope it helps, and good luck!