they can be expensive so you might want to check out craigslist, i found one on there and just picked it up on friday, it looks brand new it was only $35 (retails for $153.99) and is for my whole back seat so its perfect for my 2 little ones
Snoozer:
Snoozer Dog and Cat Beds, Lookout Perch Dog Car Booster Seat
btw i drive a scion tc its also 2 doors and it fits perfectly in my back seat.