A piece at least somewhat related to the adagio movement of the Haydn sonata a performance of which I "stashed" today
(erm, a link to which I "stashed" today, and will link to a PDF score later I think!)-
is his piano variations (Andante con variazioni, written 1793) in F minor, a performance of which has been uploaded to YouTube also, by Alexander Bildau
here -
http://www.youtube.com/watch?v=9dAsmRUZ2ak.
(and probably others).