Get artwork of parent album

I’ve got a lot of iTunes albums with partial artwork, where the album shows art in grid view, but some of the tracks, when played individually, do not in fact have art. I’ve tried a bunch of Doug’s scripts but (surprisingly!) none of them do the job I need to do, shown here as pseudocode:

for each selected track:
get artwork of the parent album this track belongs to
embed that artwork in this track

What would be the AppleScript to do this job?

Thanks if you can help!