filling the gap? Hmmmmm.. I have gaps every where
and I don't miss them.. don't get a lens just to fill a gap between 2 numbers! get a lens to fulfill function(s) and that may incidentally mean that you do fill the gap.
What functions/times do you want the lens for? Once you can answer that then you shall have your answer.. or give us a better chance of recommending a lens that really suits.
But if you do want to fill teh gap
that 28-75 is a nice lense!
Of course there is the nikkor 18-70, 18-200, 16-85, 35-70, 24-120 and the 24-85 they all fill the gap.
Have fun shopping for a new toy !
(BTW great idea giving stuff away so that there is an excuse to get the new stuff! )