I don't know about you but I'm really quite the OCD. But despite that, I'm still very capable at forgetting parts of my costume in the midst of all the rush.
To prevent that however, I've put together a special 'for cosplay' tin box. In this tin box, is everything I need for my hair ( except my wig cap) when I cosplay.
That includes hair pins and hair clips of miscellaneous shapes and sizes, elastic bands and safety pins.
Of course i don't use safety pins on my head, I'm just placing them in the case for easy storage.
So whenever I pack my bags for cosplay, this is the case I will always bring and be assured that everything I need for my hair is inside.
Hope this was helpful !