Sunshine Kids Easy-View Mirror Keep both eyes on the road and a watchful eye on your baby with the Sunshine Kids Easy-View Mirror. The first back seat mirror to rotate 360 degrees, the Easy-View attaches securely to the middle of any head rest. The mirror pivots to find the perfect angle to view your child without blocking rear visibility. The shallow convex shape offers the largest, clearest reflection of any back seat mirror. The Sunshine Kids Easy-View Mirror is an iParenting Media Award
Took me ages to find one of these, and this is definitely the cheapest I've seen.