Broken Tail-cap.

Basically, I broke the tail cap for my 405nm DX 200mw Focusable laser.
I know it's the tail cap because if I unscrew it and put the side of the metal on the metal at the back of the batteries it works, otherwise, when it's screwed on, the laser doesn't function.
I believe this is because of the metal on the tail cap is broken.
I wanted to know if I could buy a new tail cap anywhere or how I could repair it.

My advise, try to fix it yourself. If not, just buy a new one.