Probably time to find a new auto insurer if they can't offer assistance with your 5er. YES, I'm serious!
OK, Progressive and Foremost are known markets for 5ers. Good Sam Club has a good program. But if your current insurer can not offer coverage for your 5er it is time to look elsewhere.
Keep in mind there is no financial incentive to an agent to insure a travel trailer or 5er. It actually costs them money to service the account (commission is less than the cost of the service provided). Better to offer the entire enchilada as it were.
Al & Karyl
'08 Sunset Trail ST29RL