The official IFS Institute has a directory to find certified IFS practitioners near you.
In the United States, you can also use the American Psychological Association's Psychologist Locator to find a therapist. Though there’s no way to search for IFS therapy specifically, you can inquire about therapists individually to see whether they offer it.
You can also ask for a referral from your primary care physician or another mental health professional. Since IFS therapy is not a mainstay treatment like CBT, keep in mind that not every therapist will feel equipped to offer it.
Because a good client-therapist bond is central to this treatment, talk with a therapist you trust to see whether they're comfortable implementing some IFS therapy techniques in your sessions.