The Shackled City
Wand Bracer (3 wand version)
This metal forearm band takes up space on the body as a bracer and can hold up to three wands. Thin loops of thread fit over your fingers, each connected to a spring mechanism on one of the wand slots. If your hand is empty, you can flex a finger as a Swift action to cause the wand of your choice to spring into your grasp. You still must activate the wand as a standard action (or as required by the loaded spell).
Replacing a wand in the sheath is tricky and requires a Full-Round action. Most adventurers just drop the wand to the ground (a Free action) when they need a different one.