I'm really sorry to hear you're in this situation!
are there any online contacts you have - trans communities online - that can maybe point you in the direction of trans-friendly therapists in your area? i'm trans too and have had a couple of terrible therapists. i mean, i know the letter is of utmost importance but having to listen to that **** from your therapist does damage, and it would be great if you could find someone else, especially if you're going to see them for more than just the referral letter.
why was your old therapist not keen to write the letter?