I am not sure if I should feel ashamed, but last week I found the polishing cloth in stock in Apple Store Singapore and bought one, LOL. It costs S$29 here which is not much less than a three-course meal. The staff told me probably very few people have bought one here, when not counting Apple employees themselves. The cloth is still in stock today.
I have to say the cloth does a very good job in removing dust from the screen; one pass is all it takes. It is also effective in removing dust around the bezel gasket, and I usually took quite a while to remove the dust completely.