Or you could go the free route like me: pull the seatbelt out slightly farther than normal and twist it (right at the buckle) about 2-3" and then plug it in. It will keep it off your neck (and for the gals, it puts the shoulder strap comfortably between your, uhm, girls).
I do that on my bimmer and every rental car I am in (I travel alot for work).