Inside a box of wet wipes. Take out half the wipes, put the money (inside a baggie) in the tub, put some of the remaining wipes on top, and chuck it the storage bin under the bathroom sink with the extra shower liners and that value-sized jug of hand soap. It's such a mundane place that most people wouldn't think to look there. And the remaining wet wipes could go in a baggie in your pocket, so there's no evidence the wipes were tampered with.