Xbox 360 Controller Joystick Replacement Cap
I purchased a macro controller some time back and, unfortunately, one of the yorkies liked the taste of the thumb stick caps and proceeded to chew them off.
So, here is a replacement cap. I found the inner ABS molded piece is different on several controllers, probably due to different manufacturers. So the bottom opening may or may not fit your ABS stick. Use a boolen or resize the inner polygons to enlarge it in any mesh app so it fits your stick(s).