You basically have two options. First, you can buy the insurance offered by the rental dealership, which can be somewhat expensive depending on the company and policy. Next, you could get what's called Non-Owners Insurance
. This coverage is basically for people who don't own a vehicle but drive occasionally. The only caveat with this is it only provides liability insurance. Meaning, there is no coverage for collision
damage. Because of this, your best full coverage option might be the rental coverage provided by the rental company. Best of luck!