Velcro?

[MrForbes]

One of the first things we did was try different materials on the balls to see how they stick, and we noticed that velcro hooks appear to damage the material on the balls, so we didn't consider it for ball handling.

We are using a few pieces of Velcro, one for our electronics box cover retainer, another for holding the wireless router thingy on the robot.

[viking]

We also tried it as an assitance on our conveyor system, and found it to be very good. No disturbance to the ball. Perhaps we are using a very small amount. We also saw that there can be various strengths of velcro.