Diono Radian 3R All-in-One Convertible Car Seat, Black or Red $160 @ Amazon

Ships and Sold by Amazon. Only Red or Black is $159.99
Product Link

Also at Bed Bath & Beyond – Thanks Timnado

These are more narrow than most others which is why we switched from Britax as we needed more space in the car as the family grew. They are also heavy for a car seat, so not as easy to move around from car to car as others.