Can I use other evidence, like a model or case-based discussion, if there's a shortage of available direct experience?

Yes - where there is a genuine shortage of available direct experience, consider what you think will equip you as adequately as possible to perform this skill. In this case, ask your colleagues (especially administrative staff who will be taking calls) to direct any future patients to you who are enquiring about female barrier contraception, consider online resources such as the Caya demonstration video on YouTube, ask senior colleagues who may have experience of fitting female barrier methods to share their wisdom with you, practice with a pelvic model, go to a pessary clinic, occasionally you come across a patient who has used one in the past - ask them about it, etc etc. Discuss and agree your plan with your educational supervisor and ensure that it is flagged in your Educational Supervisor Report and your alternative plan clearly documented for a Level 5 signoff.