Just look up any extablished Independent Insurance Agency in your area and make an appointment.
If you plan on doing commercial video work, insurance is important. Particularly since, as you've learned, in some situations it's necessary to execute a "named insured" rider in order to cover your client or vendor's needs.
One hint: When I was starting out, there was no classification for "video production." I could either be a photographer or a motion picture production company. Guess which class had a MUCH lower premium!
Good luck.