I've never seen one for sale (Although there certainly might be one)...It is fairly simple to cut it down yourself though.
Remove the rubber tip, cut it down to size and then replace the tip.
Remember that once it's cut, you can't go back. Probably best to pick up a full sized one from your local music store and cut it back. That way you can have the cut one and a back up, full size, in case you every want to go back.