Hi FazhongDeng,
Thank you raising this concern of yours here in Microsoft Community.
The keyboard you found in Amazon is basically not a brand new one since Microsoft doesn't supply just keyboards to retailers like Amazon for Surface Book devices. The only way to find out if that keyboard will work on your Surface Book 2 is to try it out. Yes, it will fit on your Surface Book 2 but I'm not 100% sure if that's going to work. In the event that it's not going to work, you can return it to seller for refund.
On the other hand, Microsoft offers replacement for Surface Book 2 but it's for the entire unit since its keyboard and its clipboard is configured as one. It's the reason why we don't replace just the keyboard of a Surface Book device.
If this answers your question, feel free to mark this post as an answer. Otherwise, don't hesitate to contact our Microsoft Surface Support for replacement options.
Kind Regards,
Crest_Z