I sent a voice message to Simplehuman about the breakdown of the charger for my mirror, but a week has passed and no one has called me back. Where should I look for a new charger?

You can search for your charger on the Internet, but it's best to still try to contact the managers of Simplehuman and solve this issue, and if you also have warranty service, then get a new charger only through them. Do not wait for them to answer you, but contact them through the simplehuman customer service website. I wish you success.