I have a unique situation where I bought my camper as a repossession. It was 2 years old but never used- it was essentially brand new with nothing inside ever been used or turned on. Refrigerator, microwave, heater… all brand new condition. The mattress still had the plastic on it. Everyone I tried wanted to insure it as a 2 year old camper and would not insure it for the condition it was in because I was not the original purchaser.
I found RV America (who underwrites through Progressive.) They had me get an authorized appraisal and I was able to get decent replacement coverage on mine. Give them a try:
http://rvainsurance.com/
800-400-0186