My last 4 insurers have all been 2 years. Currently with Police Mutual, underwritten by Zurich, who do.
Even if its, say, one year, why pay for 3 years of GAP insurance on a 3 year loan/finance if the first year is already covered by the insurer? Wait until the end of year one is about to arrive then sign up for a further two years GAP cover.
Even better, don't get in hock for a mere car, but it's your money (or not, as the case may be).