Thank you for all contributions so far but as you all rightly surmised, I'd come across all of these before and none actually hit the spot. It is specifically an apple wand as a sign of a steward or seneschal's authority that I'm looking for, as we're not in the realms of the Otherworld or in deep myth at this point - and when the story takes us deeper into myth Kay isn't involved. And the wand has nothing to do with magic here, either - it is, simply, a sign of his authority in the way that a queen or king might hold a sceptre or an orb.
If anyone else knows more, please contribute!