I’d be tempted to go for [name_m]Arthur[/name_m] and pronounce it the Portuguese way as that seems to fit both. Other suggestions:
[name_m]Oscar[/name_m]
[name_m]Luca[/name_m]
[name_m]Alex[/name_m] / [name_f]Alexis[/name_f] / [name_m]Alexander[/name_m]
[name_m]Max[/name_m]
[name_m]Tiago[/name_m]
[name_m]Nico[/name_m]
[name_m]Hugo[/name_m]