A shawl
A good shawl can be worn when cold, easily removed when hot, used as a blanket or pillow, and cover up almost anything one could spill on themselves.

Emergency food
I have some eating restrictions and its easy to panic if things go awry. Having some Kind bars or Lara bars, nuts, or rice crackers can make all the difference in keeping my cool.

Foam earplugs
You never know where you may end up having to sleep. See shawl above.