Arlo is fun and unexpected—good idea! [name_u]Chase[/name_u] is cool too. Maybe [name_u]Les[/name_u]? All the letters are there…
You could always have a nickname that’s not actually related to his name, like [name_u]Sonny[/name_u].
Or use the middle name. Like if it’s a J name, he could be CJ.