Blue Sky is often mentioned here. I settled on FCIS, out of Iowa. They do agreed value insurance and although I haven't had a claim with them, they are easy to do business with.
FCIS Insurance - Iowa Life, Auto, RV and Pet Insurance Company
I pay $600ish for $55K of agreed value coverage. They will need an appraisal as your unit ages, but probably just your bill of sale for a new unit. Even though yours is new, I would pursue agreed value, as you would take an unjustified "hit" even during the first year if your unit was totaled.