David Petrie lists quite a few options (including one shared earlier on this site) to keep gapfill tasks fresh and useful.
Leahn Stanhope has compiled some excellent ideas.
Nik Peachey has found a seemingly excellent resource in Vyou.com.
…not even an initial text. Mike J Harrison shares his great idea (though I think you could do it without lying to your students!)
Priscilla Santos summarises the recent #ELTChat on this seemingly very common problem, via Marisa Constantinides’ blog.