@ Ben and the Pedants
I feel I may be leaving myself open to the pedants' revolt but, strictly speaking, MS' is just as correct as (presumably the expected) MS's. This is similar to wanting to show the possessions of James with James'. This does not mean several Jameses and in most contexts is adequate and most importantly unambiguous. Similar complaints have been levied at the use of women's instead of womens' but the plural removes all necessity for the latter usage.
I agree that the spelling mistake is tragic.
Don't even get me started on stadiums vs stadia!