I have an IS250 and have this Thule one, like it, fits great on the car. It's really heavy though. Make sure you place the lower part on the trunk as directions state and not let it rest on on the bumper! You can find them on sale through out the year. I think the lower priced Thule models would be just as good and not so heavy.
http://www.thule.com/en-us/us/products/carriers-and-racks/bike-carriers/rear-door-mounted-bike-carriers/thule-raceway-pro-9001pro-_-1685473