The first idea was to wire the switch and the battery into a bracelet where it would be disguised.
I ended up cutting some of the wire out of the circuit and re-soddering it. I then balled up the circuit and embedded it in a ball of epoxy putty at the end of the wand with the switch sticking out on one side and the battery accessible from the other. The ball was almost entirely hidden in the actor's hand and she was given much more freedom of movement.
And then I added sequins because...they're pretty and when the lights hit the blue sequins it made the wand even more magical.