Don't overlook the waltz syllabus and song list on this site on the Learning the Dances page. It is usually listed at the bottom of a specific dance page. It may not be what you are looking for, but there might be a couple of good instrumental selections in there.
My studio uses an entire waltz CD that is all instrumental, but I just don't know the names of the songs.
Posters on this site are quite good at recommending specific songs, and some should come up with good instrumental versions.