Artisan soap from Yemen is worth adding because it feels like something you actually noticed while travelling through Yemen, rather than a generic souvenir. Small bottles are best. A local scent, soap or oil feels personal, but it is still easy to pack and usually does not cost airport-perfume money. I would look for it in a proper local supermarket, covered market, deli, pharmacy, gift shop or small producer rather than leaving it until the departure gate. Back in the UK, it is worth checking specialist shops first because they often stock a better version than a broad marketplace listing. The ideal version is modestly priced, not too bulky, and good enough that you would buy it again even without the holiday memory.