If they’re a normie coffee lover, whatever brand of preground 100% Kona the store has the most of should be fine. In Honolulu, Don Quijote in town and the Keeamoku Walmart have shitloads, just make sure it’s 100%. Can grab a ton of random souvenirs and gifts while you’re there too.
If they’re a Reddit coffee lover, stop trying and just ask them what local specialty brand they want. It’s gonna be whole bean for sure and anything else will disappoint them secretly.