Nikon Lens Pen

As far as I can tell, this is just a generic lens cleaner, and I happened to have bought one with "Nikon" stamped on it.

At one end it has a fine brush that is retractable, and at the other it has a moistened cleaning pad under a cap (the cap has the cleaning solution in it.)

It actually does a really good job, and I'd recommend it.

Get it here.