Never heard of travel insurance for camping. Each CG has their own cancellation policy. Read it before you book and make a decision. Usually, if you cancel far enough ahead you can get your money back - or at least with a small fee. If you cancel the day before arriving I would assume you eat the cost. The CG needs time to be able to rent that spot otherwise they are the ones who lose money. I have seen cases where they would not refund it and folks can "sell" their reservation to someone else who is able to take it.