When I was young and had fast cars I would get my father to do the insurance with the policy covering all drivers, or me as a named driver. With a limited mileage policy that should be the cheap option and you are covered. Of course there's always the risk that if you have a serious crash the insurance company will be asking questions, so do it at your own risk.
I wouldn't be surprised if you have real difficulty in finding someone to cover you at that age. Even under 25 is not easy.
Good luck.
Charlie