Agreed, may be difficult to get hold of, looks to be an OEM-only product.
Windows Server Essentials is available through our OEM Server Hardware partners.
https://www.microsoft.com/en-us/windows-server/pricing
You can call them directly here.
https://support.microsoft.com/en-us/topic/global-customer-service-phone-numbers-c0389ade-5640-e588-8b0e-28de8afeb3f2
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