A simple, economical and easy wishbone is the one in texture, if one knows how to make the right knots needed.
The wishbone in texture is simple and economical, possibly to be made in Dyneema. One has to take a 12 cm long Dyneema line and make two knots, one per end. Once the knots are made, the line has to be burned at the ends to avoid it from ravelling. Finally, the two knots, after soaking them with water or saliva, are inserted in the hallow central part of the elastic bands of the sling gun. In the below video the tutorial for making the correct knots.