Submitted for your consideration: The Altec-Lansing Orbit 227.
I wouldn't claim this to be "The Best," but I will claim that it's absolutely the best $13 alternative you'll even find:
http://www.amazon.com/Altec-Lansing-iM227-Orbit-Speaker/dp/B004CYKEBK.
It runs 24 hours on three triple-As, and sounds surprisingly good for non-critical listening. I've got four of them scattered around and they're a cool little piece of gear. Even comes with a padded case and a carabiner clip to hang it one your belt, should that appeal to you.
The link will get you just under 800 reviews, so it might be worth reading through a few to see if this bargain alternative will do the trick for you.