Microsoft no longer supports Access 97. You cannot buy a license from Microsoft. Legally, the software is considered "abandoned," though the copyright is still owned by Microsoft. Enthusiast communities generally consider downloading Access 97 for legacy hardware as "low-risk" grey-area activity, though this is not legal advice.
First, let's clear up the terminology. Microsoft never officially released a "portable" version of Access 97. The term refers to a modified or repackaged version of the software that can run from a USB flash drive or a hard drive folder without being formally "installed" into the Windows Registry. microsoft access 97 portable