Spares to bring to a track day
When you go to a track you have to plan for the very real possibility of a crash. Crashing sucks, even at a track, but if you have the right stuff you will stand a better chance of getting your bike re-operational and being able to take advantage of the rest of your day. It beats going home.
Here are some generally recommended items to bring. If you are making a habit of going to the track, you might want to keep a box with most of this stuff in it.