Delgado's answer is correct that MP4Box can do this, but the
-par option doesn't work quite as described. With an
-out parameter (so as not to disturb your original file):
mp4box source.mp4 -out target.mp4 -par stream-number=width:height
When you use
-par stream-number=width:height, you define the pixel aspect ratio – that is, the result of dividing the device aspect ratio by the storage aspect ratio. (Equivalently, you're describing the aspect ratio of a source pixel.) For example, suppose you have a DVD source that's 720×480, and the correct display aspect ratio is 4:3. For this case, you need:
mp4box source.mp4 -out target.mp4 -par 1=8:9
because (4/3) / (720/480) = 8/9.
If the source represents true SD NTSC pixels (in which case only the central 704×480 pixels are supposed to map to a 4×3 screen, with 8 pixels overscan on either side), the correct command would be:
mp4box source.mp4 -out target.mp4 -par 1=10:11
because (4/3) / (704/480) = 10/11 – exactly the reference pixel aspect ratio for standard definition NTSC video.
For the case given in the question, if it's really 4:3, that gives a very odd pixel aspect ratio: (4/3)/(720/416) = 104/135. It's 720 wide, which suggests a DVD source; it's a 25 fps video, suggesting PAL, but the PAR works out to less than 1, suggesting NTSC. It could be 4:5, I suppose (very close to 104:135), but I don't know of anything that produces that pixel aspect ratio; maybe try that first, and then try 3:4 if it still looks a little too stretched horizontally. If you're certain it's exactly 4:3, of course, just use 104:135.