Passive exoskeletons that support the weight of the surgeon’s arms could yield a significant ergonomic improvement in the Laparoscopic theatre. However, the cost and regulations associated with sterilization complicates adoption of such devices. In this work a compact passive arm support mechanism is designed that can be worn underneath the surgical gown to circumvent sterility requirements. The design utilizes shape optimized compliant shell mechanisms who’s geometry can remain substantially close to the body as well as achieve the nonlinear stiffness characteristic that is desired for balancing the arm’s weight. A shell design with the desired torque-rotation characteristic is designed using shape optimization and fabricated for validation testing. Measurements show the prototype balances 19% of an average adult’s arm weight within ±4 percentage points between 0 and 90 degrees of arm abduction and or flexion. A prototype of the mechanism remains within 34mm of the arm, nearly twice as compact as the state of the art.