Sometimes you can appeal to the insurance company if they do not have a suitable physician for you. Bronchiectasis is a rare disease, with a limited pool of experts, and M. Kanasii is very rare.

Maybe using the information in the link I provided can help you get either the pulmonologist or primary to refer you "Out of Network due to Medical Necessity"?

Also, here are the current protocols regarding when/how to treat - you can demonstrate that the doctor is clearly not following them.
https://ntminfo.org/wp-content/uploads/2020/07/NTMguidelines2020.pdf
They are a lot for a layperson to wade through, but what the clinicians and insurance need to see. New guidelines are due out soon, we just don't have a date yet.

Finally, here is the current NTM/Bronchiectasis Centers of Excellence listing - more practitioners will be added as they clear the approval process.
https://connect.mayoclinic.org/discussion/the-bronchiectasis-care-center-network-33-centers/
I hope you can find some help.