I'd say this kind of depends on the effect you're going for with it--if it's to goad opposition into doing something, I'd say it's a maneuver on them. If it's to block them from paying attention to your legit magic items, then, well, it's a straight up block against perception.
Honestly, I'd say that's the easiest way to do it--make it a one-slot enchanted item with either a block or a maneuver to that effect built into it, if it's always going to be centered around this one staff.