There are a number of companies that provide a complete estimating and supplementing service. 3% of the claim is a rather customary charge.
First though, you need to understand the estimating and supplementing starts with you. It starts with your inspection, roof graphs and damage photos. Don't expect something magical if you don't provide the estimating/supplementing company with all the things they need to do their job properly. I've tried helping people out a few times and it is my experience they hand you a bucket of chicken shit and expect you to make chicken salad out of it. Ain't going to happen.