Saybrook University is a good place to start. See their website at http://www.saybrook.edu/areas-of-study/humanistic-clinical-psychology/
Sofia University has a program in transpersonal ... http://www.sofia.edu/academics/graduate-school-of-transpersonal-studies/doctor-of-philosophy-in-transpersonal-psychology/
APA Division 32 has a website on how to become a transpersonal psychologist at http://www.psychologist-license.com/types-of-psychologists/transpersonal-psychologist.html#context/api/listings/prefilter
For training programs in existential, see the website at http://www.existential-therapy.com/resources/training-in-existential.html [training in Existential-Humanistic Psychology]
I think Dragos is right... you should look for scholars in the field with whom you would like to work/learn and look for training oportunities with them!