ferry from Zadar to Slovenia

We will be in Croatia in Sept – Oct finishing in Zadar, we would very much like to take a Ferry into Slovenia, but have had no luck finding one

You may be able to take ferry from Zadar to Pula (Istria) as this line will be reintroduced in 2017, and then ferry (or bus) to Slovenia.
Here are the ferry maps:
https://www.croatiaferries.com/maps/italy-istria-ferry-map/
https://www.croatiaferries.com/maps/north-adriatic-local-ferry-map/
and schedules info:
https://www.croatiaferries.com/zadar-pula-ferry.htm
https://www.croatiaferries.com/italy-ferries.htm