Seriously, stick a screwdriver in the end, hold the ball in your hand, tighten as much as you can.
Problem solved.
The only way you can then remove the ball/bat is if you can grip the shaft tighter with your hand than you can with a screw driver in the slot.
Fair enough if you are a 7 stone weakling then maybe some blue locktite maybe the solution for you (you may have to ask a strong friend to remove the cap though)
[Just FYI, please keep the first sentance in context with this thread!]