Yeah he was like "Are you sure this isn't permanent?" Even though he's seen that my full hand one has gone...duhh what a worrywart lol
I get mine from my local Indian Grocer, they're so lovely and her daughter does some beautiful ones. You can probably find them at most Indian grocers, some dairies may also stock them. They're usually around the beauty products or the devotional items and incense.
Cost is around $2-3 for the mylar cones which I think are the best in terms of getting a nice clean thin flow, and handling. The henna should be of a thick consistency like toothpaste. The cone colour may differ in both pattern or colour, I have blue and green as well, but the henna inside is all the same.
I'm wanting to get a full hand one done again, so I'll post pics of that when I get it done.

Stay away from the plastic tubes of henna, I bought a few of them and they were utter shyte. They were runny, it wasnt real henna, but some kind of runny red dye. What a mess it made. Lucky it was so crappy as it was gone in 2 days after scrubbing.