looking to find and insurance comyany that does liability for form work shuttering carpenters?

Where are you located? Companies are licensed by state. I would recommend contacting an independent agent (the handle many different companies) and select one the specializes in commercial insurance.

Start calling local Independent agents. If you try someone and the first name you see is an insurance company you know, they probably won't be able to help you. If the name of the agency sounds like an actual person or family, they will be able to quote this for you.

If you don't go through your professional association, you cannot buy this directly, bypassing an insurance agent.

So, start with the guy that sells you your car insurance. Get some quotes. Likely, it's going to cost more than the quote you already have.