The BEST thing I found is those shower loofas/bath thingys. Don't know what to call them, but mine is white, has a rope on it (for easy pulling out of the bottle) and is the same material as the yellow thing that comes with the bottle. It never moves, and is just as easy to pour liquid over.
Great tip, I am always losing things too. Not just on the road. I always seem to be throwing those shower puffs out (or whatever they are called) as they are always free givaways with body wash - what a great use!