Maybe not. There was some bad blood between the Neuburgs and the Habsburgs - originally the Empress Eleonore and her brother wanted Josef to marry an unspecified cousin (might be Elisabeth, but I would be thinking more one of Eleonore's youngest sisters), and Josef went against them and married Wilhelmine instead. Now, of course, that cousin might be married to Leopold instead, but it could just as easily lead to conflict between the Pfalz-Neuburgs (they only became Electors Palatine after the POD, so Karl II might live a smidge longer, if he leaves kids with a half-crippled wife is anyone's guess though) and the Habsburgs.
My favourite would be a Danish princess. Leopold I angled for Josef to wed Sofia Hedwig OTL, now Sofia might be a little too old for Leo, but she had a stillborn sister in 1683, who may/may not survive. Or her brother Vilhelm could just as easily be born Vilhelmine instead. The reason the wedding negotiations foundered was because Sofia refused to convert. Have her little sister be more pliable and bam! Danish-Imperial match.
Otherwise, Elisabeth Auguste's cousin, Maria Anna Karoline might make a better match. She's in theory the heiress to Saxe-Lauenburg (yes, I know Leopold signed away Anna Maria Franziska's inheritance), which is a sight better than the heiress to some lands in Lithuania. And she's fertile - she married at 26yo and still left two boys and a girl who survived infancy.