The International Society for the Study of Trauma and Dissociation (https://www.isst-d.org/) (ISSTD) "seeks to advance clinical, scientific, and societal understanding about the prevalence and consequences of chronic trauma and dissociation." The ISSTD has a searchable therapist database here (https://isstd.connectedcommunity.org/network/network-find-a-professional).
Note: The ISSTD is different from the The International Society for Traumatic Stress Studies (https://istss.org/home)(ISTSS).