I saw this on the eBay site, although I can't find any for sale. In this article "option 3" appears to be a kind of sanding sponge:
http://www.ebay.com/gds/Ouch-Sharp-F...4719643/g.html
It looks like it would be good for my project which has an unbound, unfinished rosewood fingerboard. So, is this an actual thing? Has anyone tried this? I can't find a "Banana Yellow Fret Edge Buffer" anywhere.