Any place that sells hunting/archery equipment or a hobby shop that has stuff to make the little model trains or doll houses should have the tips. You can also get them from Sharon Schambers website as a PP said however I have NEVER seen them in stock there!
There are two pieces a plastic piece that gets screwed onto the bottle itself and then the metal tip that goes over that.
I just don't open the orange screw cap up all the way! lol