The search for "Autodesk Fusion 360 Portable" is a ghost hunt. It is a desire for an old-world software model applied to a new-world architecture.
: Free for hobbyists, but limited to 10 active documents and basic 2.5 and 3-axis milling .
Since there is no official portable executable, the best way to maintain mobility is: Fusion Team (Web Browser):
Treat “Fusion 360 Portable” as a mindset: curate the minimal, critical assets and workflows that let you be productive anywhere while respecting licensing and keeping your toolchain consistent.