Hi @Ahmed Mostafa ,
as far as I know the wireless keyboard and the dongle are paired by default and are always sold together.
This makes a replacement impossible.
You can get in contact with the Microsoft support for hardware here: https://support.microsoft.com/en-us/account-billing/contact-microsoft-store-support-4f615f2a-6bbd-fd69-6695-ae213d63eef0
Maybe they are able to help.
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Regards
Andreas Baumgarten