I was recently reminded of a tool I use for other medical conditions and realized I will do this for migraine also and share with you all.
Pocket cards and badges/buttons.
For any ailment you can create a pocket-sized card with a brief explaination of condition symptoms and/or needs.
Many conditions have card templates or cards for purchase online.
One source is
http://stickmancommunications.co.uk/
These are very handy as quick explainations, or when symptoms prevent you from even being able to explain yourself, and they lend gravitas to the importance of treatment/accomodation you may need.
Hope this helps!