There is no official "portable" executable from Microsoft for Office 2019.
Note that Office 2019 products require Windows 10 and will not run on older versions of Windows. Techsoup Moldova Where to enter your Office product key - Microsoft Support ms office 2019 portable version no need to install top
If your goal is to avoid cluttering your computer with a heavy installation, consider these official "no-install" or low-impact methods: There is no official "portable" executable from Microsoft