This is the blackened-purples department (although both of these seem to lean blue-ish) - OPI Who Are You Wearing? and Color Show Amethyst Couture:
Both of these polishes are pretty definitely unavailable. Apparently Who Are You Wearing was from OPI's 2007 holiday collection, and it hasn't become enough of a classic to stay in the main collection all this time. If you scroll down on the link above, there's a comparison with Russian Navy, which is more blue, and also Essie Midnight Cami, which I have and which I wouldn't really put into the blue-violet category at all. It's much more blue. (I'll probably get around to that one in the next couple of weeks, I'm guessing.) Anyway, Who Are You Wearing? - basically a straight very-dark blurple except for some shimmer. It's so dark I don't think the shimmer shows up all that much, though.