New therapy certification

I’m wanting to go for a new therapy certification. What would you psychiatrists say is the hardest therapist to find? I feel like every one and their brother/mother/sister are trained in EMDR these days, so not that. What about CBT-I or ERP?

For context, I’m a licensed therapist in Oklahoma but am moving to Chicago in a month, so if you have familiarity with Chicago specifically, that would be a bonus.