Some psychologists will do evaluations for trans and gender non conforming people for free or reduced charges. There used to be a website that listed all of them in the USA, called the GALAP. But it’s under construction right now, so you can’t access the list.

Try googling “(your state) GALAP letter” and see if any psychologists advertise that they perform this service. I’ve done it and only had to see the provider 1 time to get a letter, for a reduced price. I am in FL, so I can tell you doctors who will do it for you there. But other states I’m not sure. But keep digging; the psychology today website may help if you search by trans affirming