i smile at him but i don't know if he can see because he's pretty busy being nervous
The next time you see him, a off-hand "i like the keffiyeh/scarf you've got on" would show a lot of solidarity! It usually only takes one random compliment from a stranger to help people get past that initial 'I look like a dweeb' nervousness with any sort of attire/accessory.
If you've got an Instagram, follow their account and turn on post notifications. They usually make a post announcing a restock like the day before/day of. https://www.instagram.com/hirbawi/