Opteka is now offering a shoulder rig stabilizer. Very basic with a pair of straight rods, shoulder pad, mounting plate, cross bar, and two handles. A decent set up to minimize rotation. Claims to be made of heavy duty aluminum construction and standard 15mm compatible (for most accessories). You can find it available following the link (click here).

Opteka Shoulder Rig Camera Stabilizer 15mm

Also available via Amazon below (click here)

Opteka Shoulder Rig Stabilizer