How to fix this

Wow. I don’t usually hear of power buttons spontaneously popping off. Did I understand that right? Or did it break and stop working?

You can generally look for tablet repair shops. They can order the part online. This is what most repair shops do. Unless it’s a popular part,they order it online and will replace it for you. It may take a few days to a week for the repair to finish. There are places you can mail your device to,to be repaired. But if you can find a local repair shop,that would be your best bet. Call them,tell them the issue,be specific and ask if they can look at it.