Fresno, closest big city to me, has few restaurants that offer it and frankly I don't think any of them have top quality ciopinno.
pretty sure I posted about a restaurant my daughter found in Napa, (close to you?). It's called "Pasta Prego". Small restaurant. My daughter had the Mussel Risotto - came home and said I had to try it. I think it was two days later we drove to Napa for the Mussel Risotto. It was worth it.