When I purchased my K2 Superfrees, I got a really good deal on the brand new, in plastic, flat skis since they didn't have the bindings with them.
Normally, the Superfrees come with the Marker ER3 10.0 Bindings (essentially a system binding). However, I could not find this model of the binding on Marker's site. I know I don't have to get the exact same bindings; however, the ER3 is supposed to have some advantages.
The K2/Marker ER3 (Energy Response Plate) is designed for advanced and recreational skiers alike. The ER3 is also shorter and less stiff than the men’s system, allowing the ski to flex more smoothly while reducing more than half a pound in weight. This system utilizes a new 20% lighter Compact Toe and a fixed Compact2 Heel design to generate more power, precision, and quickness underfoot.
I can only find the EPS on their site: