Yes, there are multiple templates and business cases available for potential outsourcing frameworks. IACCM offers its members access to a wide range of standard templates which can be used as-is, and/or adapted to include elements specific to companies on a case-by-case basis, so we should learn more about the specific requirements, needs and size of your organization prior to analyzing templates for those purposes.
As Pablo has indicated there are multiple options, as a business case will be highly variable and largely depend on the structure a given enterprise expects of their business cases across the enterprise. Plus, the business case will largely depend on the nature of what is being outsourced. With these variables in play, someone else's business case might not be an ideal for your purposes - it will have limitations and should not be treated as the solution. Rather, it is best utilized as a general starting point. Has your enterprise created business cases for other endeavors? Those internal templates should be consulted.
With these caveats aside, you are encouraged to join the IACCM Community of Interest (COI) focused on Outsourcing, as there are probably a few members in the Outsourcing COI who can share some specific examples.
Thank you very much, i will join the IACCM Community of Interest :)