How to buy Microsoft Defender for Endpoint P1‎ standalone license SKU

Hello,

I have started a Microsoft Defender for Endpoint P1 trial via the Microsoft 365 admin center.

But I cannot find any option to actually buy Microsoft Defender for Endpoint P1‎ standalone licenses.

Although several Microsoft pages mention that Microsoft Defender for Endpoint can be purchased as standalone license (https://learn.microsoft.com/en-us/microsoft-365/security/defender-endpoint/minimum-requirements?view=o365-worldwide#licensing-requirements)

How can I buy standalone licenses?

Thanks