BAL Accu Glide motor/gear coupler replacement problem

On a Montana 3725RL there is an electric slide system by Norco for the bedroom slide. The installed unit on my 5th wheel has a Yifan motor and gear box that uses what appears to be a 1/8"x1/8"x2" spring steel flexible coupling.I need a new coupling but cannot find one anywhere. A piece of 1/8" sq. keyway works as a temporary substitute but may shear or twist with pressure. Anyone have any experience with this problem?