As there may not be an existing OER you can adapt, you may be interested in creating your own OER.  You can do this independently but do consider collaborating with other colleagues in your field.

Here is information about OER authoring tools.

• Authoring Open Textbooks. From the Open Textbook Network, this guide includes a checklist for getting started, case studies of publishing programs, textbook organization and elements, writing resources, and an overview of useful tools.
• Modifying an Open Textbook: What you Need to Know. Also from the Open Textbook Network, this guide  focuses on the technological aspects of editing open textbooks found in the Open Textbook Library or elsewhere, and will help you assess the effort, expertise, and technical tools needed.
• Guide to Developing Open Textbooks. Produced (August 2016) by the Commonwealth of Learning (COL) and released as CC BY SA. 66 page guide presenting technical advice for textbook development in a variety of platforms and formats.
• BC Open Textbook Accessibility Toolkit. The goal of the Accessibility Toolkit is to provide the resources needed so that each content creator, instructional designer, educational technologist, librarian, administrator, teaching assistant, etc. has the opportunity to create a truly open and accessible textbook.