Many medical organizations require a licensed psychologist to write the prescription for ADHD medications, rather than the attending PCP, and many insurance plans don't cover psychologist visits.
It would be a psychiatrist, not a psychologist.
And all insurance plans do cover mental health per the ACA... It is one of the ten benefits that must be covered on all plans under the law.
As a psychologist, my experience is that lots of physicians, even psychiatrists, want testing and a diagnosis from a psychologist before prescribing, so it might look like the psychologist is prescribing, when they are just diagnosing.
Incidentally, psychologist prescribing happens in some states also.
Just do it, it's really not that hard. Lots of patients (especially with ADHD) go off their meds for long periods. If anything, it's a sign that the diagnosis was correct.