Try some stick-on nail polish. It's available at other places, other than HT, but not in black.
http://www.hottopic.com/hottopic/Acc...als-216661.jsp
I know it has doodles on it, you can always sharpie that out.
http://www.hottopic.com/hottopic/Acc...Set-298955.jsp
That's neat too. If you don't fancy the blue and magenta, either save it until you do or give it to someone else.
BTW, with that set, the site's instructions are vague. What one ought to do with that is use one of the nail polishes and then put the sticker on over it, where the sticker fits into the bottom of the nail bed. It depends on how long you want your nails. If you want the French manicure look, go for that look by growing the nail out a bit, painting it black, and using the stickers.