I know this doesn't answer your question, but don't waste the money. I too am quite obsessive about keeping my gadgets pristine, but unless you plan on buying a replacement, and then spending more on a whole case skin to further protect it, you're likely to scratch it again... it's the bottom of a laptop.
Bear in mind as well that the bottom of a mac laptop carries the serial number, so if you find a replacement it will either have the incorrect serial or have it "removed" somehow.