We were at WDW over Thanksgiving and saw nothing we could buy that said VMK -- no pins, no shirts, nada. (We did, however complete all four in-park quests, for which we received wrist bands and lots of cards!)
In VMK Central they told me that the Emporium had shirts on weekends, but nobody in the Emporium this weekend knew anything about that. They told me to check in VMK Central. (One cast member tried to explain that the VMK was "virtual" and just in my computer. Ohhh. Thank you.) I commented to several cast members, including one of the survey takers, that they were really missing the boat in this regard.
Maybe by our next visit...