You probably will not get insurance for a period of less than a year. As the good Rev says the only way out for you may be to you pay for a year and try for a refund when you cancel it. But check what the cancellation conditions for refunds are.
I recently transferred a car to a family member who then took out her own insurance. I was left with approx. two months of unused insurance cover and I applied for a rebate. The nasty surprise I got was that the cost of changing the terms of the insurance contract exceeded the value of the rebate so the cheeky sods sent me a invoice for the difference!
I kid you not