Hello Peter!
There is no such sound set yet, as it would be an elaborate task to create it and I'm not sure how many users out there would actually use it.
Mallets can be used easily without a sound set. For all unpitched percussion instruments there is a workaround to have all the articulations at hand without a sound set. Here is an excerpt of the "Optimizing Sibelius playback" manual you find in your User Area under Overview/Needful Things/Sibelius Sound Sets:
Best,
Andi
Vienna Symphonic Library