CTOMS has a new casualty litter available. The Foxtrot™ Litter is small enough that you can attach it to your ruck (though that's an obvious trade-off for weight on the back and weight on the feet).
According to CTOMS it "...provides an effective casualty evacuation platform that is quick and easy to employ and is compact enough to accompany individuals on an assault or long movement. It is small enough to attach to your pack, but is still functional in a combat or rescue environment. It provides a rapid means of casualty movement without compromising durability, flexibility, or the individual's ability to maneuver through the most demanding environments. Casualties can be dragged or carried off target without excess time spent rigging and securing. Color-coded side release buckles provide an ideal casualty securing method.''