Not sure where you are from ... like "markopolo" suggested you should look at a company that is RV specific and not just your regular car insurance carrier.
I'm in Canada and there are several companies that I could have went with. Ultimately I went with Wayfarers Insurance Brokers Ltd. They are underwritten by Aviva Elite. One of the selling features for me was that I have complete replacement cost for the RV for the first 5 years.
I also imagine that your RV dealer will have some suggestions for you ... but by now I imagine you already have your unit and are enjoying it.