Jonathan's experience might be very common: you search the literature in order to find helpful references for your course, but sometimes it happens that you cannot find something that suit your learning objectives, or the scenario in which you are going to work with students. He chose to refer to his field literature and it worked, since he was able to find activities which were consistent with the aims of his course, and he could adapt them to make them fit even better. In other cases, the most effective solution is to look outside of the box, and search for examples or activities applied in fields that are far from yours. But the most important thing is to start somewhere and try!