Hey Kathy,
Have you explored the "Report Collections" functionality on the Projects tab within TBM Studio? This feature allows you to select report collections and specify which roles can see that report.
Additionally, when creating new reports, you have the option to specify which roles the report will be exposed to, for example, Admins vs Business Users vs Finance Users.
Depending on how your security is set up currently, this may not require much additional effort, just identifying which reports you'd like to segregate, and getting the right folks in the group.
-Ed