my 2 cents

bittrex - probably because it used to be called pimp, they stated they wouldnt add coins with an offensive / derogatory name (from gimp thread)

Polo - isnt this a mint? jk i dont really use em so no idea

anyhow we have cex and bleutrade i'd imagine bittrex will be adding it soonish though more volume or a bribe seems to be the best way to get there