I haven't been able to find it either, but the way Gore phrased it in the debates, and the absence of reaction by then-candidate Bush, leads me to believe that then-president Bush was the first (of the two) to say that.
I'm still looking for old transcripts that substantiate my belief. As I noted, if anyone has a repository to campaign speech text, my offer to review it stands.
There's an important distinction between "in the mold of Scalia" and "strict constructionists". The first seems to paint the picture of those who would vote lockstep with Scalia regardless of principles. The second says they would be true to the written Constitution.
Gore was trying to paint that word picture rather than recite a true Bush quote.
But I agree with you that if someone can produce a quote of Bush promising to appoint people "in the mold of Scalia" then I'll accept it.
However, appropos of the current discussion, when President Bush hinted that Miers would vote the way he would like, he was painting his own word picture of someone who would vote lockstep regardless of principle. Whether he meant to or not.