I suspect there are hundreds of such works. I went through an old ASCAP catalog, and there were lots. I don’t know if you can search their online catalog by instrumentation, but you might be able to go composer by composer and use harp as a keyword.
I have “Concertino in an Old Style” by Maciej Malecki, published by Salvi, for strings and 2 harps. Then there is Sospiri by Sibelius, a very short piece and the Adagietto in Mahler 5 of course. I’ll keep thinking…