you can get little USB-PD boards for really cheap! just solder a jumper corresponding to the voltage you want and swap it in place of the stock power connector. its trickier if you need to enlarge the opening for the connector, but the one on the magic wand matches the size of a type-c port rly well

modding a usb type-c port into my vibrator is undoubtedly the most useful project i've ever done