CCM,
At first I used silver bolts but later ordered black carriage bolts from Bob Roberts. I think the ones I used for the joysticks are about 1" long, maybe 1.25". They are size 3/16".
jakejake28,
Yes the balltop can be unscrewed. I'd dye it before trying to paint it though. I've had good luck dying some plastics in the past and I think it would probably work well on these balls.
Wade