Michael's carries the Versamark brand. If you want a more metallic looking purple, take a look at Brilliance or Encore brands. Encore is slower to dry than either Versamark or Brilliance, and all three don't dry as well on glossy/slick cardstock as they do on matt stock.
Any of them look really nice stamped on a slicker cardstock and embossed. Have you ever tried embossing? You get embossing powder and a heat gun. Stamp your image, then sprinkle the embossing powder on it like you would glitter on glue. Shake off the excess and then zap it with the heat gun so the powder melts. You get a shiny raised effect. Looks really cool :-).