You've already written your representatives in Congress about the Western Sahara, and you've still got stamps left over. Write to Morocco's ambassador to the United States, Aziz Mekouar.
Besides looking dashing in a fez, Ambassador Mekouar likes to present Morocco's interests, including the continued occupation and economic integration of the Western Sahara, to the United States. Special points if you congratulate him on knowing six languages.
I've sent the Ambassador two letters, one on Thank You stationery left over from graduation. I haven't received any replies. Even if the letters never even get to Mekouar, they make clear to Morocco that Americans know about the Western Sahara, and make its representatives in the United States more cautious when dealing with Congress or the President.
Address:
Ambassador Aziz Mekouar
1601 21st Street, NW
Washington DC 20009