Summary

I made a fast and very simple gripper to test with my CyBot :
https://cults3d.com/en/3d-model/gadget/cybot-cycloidal-disk-robot-arm

You can use it for different robot arm with small adjustment
You need a nema17 and a T8 screw to be cut at the correct size.
If needed you also need a joint between the nema17 shaft and the T8 screw with copper nut , take a flexible 5mm to 8mm coupling (check nema shaft first)