Insurance Recommendation (US Based) for Aerial Lift Training

Hoping somebody can help me out with something that feels like I can’t find a good, direct answer to. My father-in-law does Operator Safety Training for aerial lift trainings and forklifts. He is looking to get insurance but has had no luck finding what he thinks would be best, and from my search I could only find something appropriate in the UK which does not help lol. Any help or guidance is greatly appreciated!