Any Ideas on Cheaper Insurance for extra car?

My 2000 Saab 9-3 Convertible is an extra vechicle. My wife and I have a total of 3 vehicles and only 2 licensed drivers. Anyone know of any cheaper insurance you can get on the Saab to use it as an extra/hobby type vehicle? Is there good insurance available thru the Saab Owner's Club or something like that? I would like something where you agree to not exceed a certain total mileage for the year, or something like that. Any ideas?