@AMye1 ...
There is a paid product from Cidi Labs (the makers of DesignPLUS, ReadyGO, and UDOIT that you may have heard of before) called TidyUP, and it does exactly what you are looking for. TidyUP scans your entire course and looks for unused content and files that are safe to delete so that you can free up space in your course(s). You can find out more about it at:
TidyUP for Canvas File and Page Cleanup | Cidi Labs
Since this needs to be installed at the Canvas account level, you'd want to talk with your school's Online Learning / eLearning / Distance Education team or your Canvas administrator to see if purchasing this would be an option now or in the future. They would then reach out to the Cidi Labs team (they are great, by the way!) to line up some initial conversations, possibly schedule a demonstration, and talk about pricing for your school.
I hope this will help a bit. Good luck to you!