Hi, I was in Sydney a year ago and looking for the same activity to do - Koala and kangaroo encounterskangaroos and koalas.
After searching I found few day tour companiesday tour companies do that for varies rates. I will share those links here and you can have a look -
There is a company I found do the Blue Mountains Private ToursBlue Mountains Private tours that include kangaroo encounters. https://www.sydneytoptours.com/Blue-Mountains-Tour/.
There were another company who do the big day tours to Blue Mountains from Sydneygroup day tours to Blue Mountains from Sydney and link is https://www.bluemountains.tours/

Hope this will help you in your research.

Travel around Aussie is great and many things to se and explore. My favourite was Gold coast, Melbourne and Sydney. I am real wine lover and Hunter Valley in Sydney and Morning ton Penning Sula are my favourite areas for wine tasting. If you are after a good tour company who are really good at wine tours, try these guys - Hunter Valley Private ToursHunter Valley Private Tours by https://www.sydneytoptours.com/Hunter-Valley-Tour/ or https://www.huntervalley.tours/. Both companies own by Sydney Private ToursSydney Private Tours and they are good.