There's no guarantee that you will find an exact OER match for your course. If you don't immediately find an open textbook that fits your needs, don't worry! A librarian can help you locate a different source or a mix of sources (of OER, library-licensed resources, or resources freely available or in the public domain) you can use to make your course affordable.
Even if a mix of materials cannot be found to suit your needs, you might consider creating your own OER.
Ask a librarian if you have more questions about:
Understanding usage licenses on existing OER
Authoring, licensing, and sharing new OER
Finding funding sources to support your OER activities
Using the Library's Course Reserves system
Finding Library-Licensed Resources for your course