I postulate that no-wield wands with basic Void Mastery do not exist.
Please prove me wrong. Any counter-example will do. I have found void mastery on void-wield wands before, but never on a no-wield wand. (I don't need a screenshot if it's actually in your possession, but I need more than "I think Bob had one," please.)
If my postulate is true, then my next question is for the devs: is this a bug or intentional? I have plenty of no-wield wands with War, Life, Item, Creature, and Arcane mastery on them. I also have Void Mastery on cloth hands and feet. I just don't have it on no-wield wands, and I would find such a thing to be useful.