A little late to this but, depending on your goals for obtaining an official diagnosis, you may not need to get an assessment. When I was diagnosed I had originally started seeing a therapist who referred me to a psychiatrist. The psychiatrist asked me some questions and diagnosed me through an interview and was able to prescribe based on that. I’m sure this varies between states.

Eventually I had to go through diagnostic testing, but only to get testing accommodations for school.

Best buy has pretty decent open box deals

Also, if you buy from apple online you can go through the education store and they don’t ask for student ID verification