Have only left side audio. Duplicate to right side?

Imported almost 2 hours of video into iMovie. However, it turned out that the settings on the video camera was incorrect and it recorded only to the left side audio. So I only have sound coming out of the left side speaker. Is there any easy way to fix this in iMovie so the same sound comes out of both the left and right side? Duplicate the left for right? If this will involve exporting the audio to Audacity or GarageBand to fix this (as I expect I will need to), how do I import it back into iMovie?

Also, I started playing with a 30-day trial version of Final Cut Pro X (days before the above issue), which expires in 18 days. If it can be fixed in Final Cut Pro X, then exported back to iMovie to do all the editing I need to do. Maybe, I could possibly do that as well. But which ever is easier. Hopefully, it can be fixed easily in iMovie.

I'm on an Apple computer with latest version of iLife.

Yes duplicating the left track onto the right track would be your best option.

Audacity is a good option as it will have the tools you need to do this.

Copy the left track to the right. Check that the levels on each track sound correct. The export the audio out as a stereo track and import back into iMovie.

I don't think you need to use FCPX as you are only working with an audio track.