This is SH Xtreme Wear Posh Plum (minus the glitter, which I'll talk about in the next entry) and an unlabeled red-violet.
As far as availability, there may be an L.A. Colors polish that corresponds to this - that's what these unlabeled minis seem to be - but I've never made any real effort to sort that out. There are a couple of current colors that look similar, though. I also took a look at Xtreme Wear colors and Posh Plum does not seem to be a current color. As I've said before, plain red-violet cremes are pretty common, but this is not a creme, and I don't know of anybody else that has a duochrome like Posh Plum's.
Posh Plum swatches here and here.