Despite the subject of the paper the appendix is a great resource for getting started making your own implicit prompts.
‘He checks in on me more than my friends and family’: can AI therapists do better than the real thing? | Counselling and therapy | The Guardian
‘He checks in on me more than my friends and family’: can AI therapists do better than the real thing? | Counselling and therapy | The Guardian
You could just run your own. There are plenty of open source models that don't answer to any company.
This is a hard fit for a goose.