I prefer it on its own because of Sir
Kai. If it has to be a nn, I like
Cairo and
Malachi, but I think they would work better with the nn spelled "
Cai".
Kyros, Chiron, Cairon, Kairon, Kairos,
Kaito,
Caius,
Kaimana,
Kaiser,
Kailash,
Kaimana, and
Makaio could work too.