Let me verify NCH's website for information on their free version and portable options. NCH does offer a free version of WavePad, which could be a starting point. They also have a 60-day trial for the premium version. There's no official portable version listed, so I should clarify that. Maybe suggest using tools like PortableApps to convert the installed version into a portable one, but note that this could be against the software's EULA, so proceed with caution.