The first thing that came to my mind is:
[name_m]Nathan[/name_m] [name_m]Edward[/name_m]
[name_m]Nathan[/name_m] [name_m]Hans[/name_m]
[name_m]Nathan[/name_m] [name_m]Aaron[/name_m]
[name_m]Nathan[/name_m] [name_u]Dale[/name_u]
[name_m]Nathan[/name_m] [name_u]Finn[/name_u]
[name_m]Nathan[/name_m] [name_m]George[/name_m]
[name_m]Nathan[/name_m] [name_m]Milton[/name_m]
These may not be your style, but a few other ideas:
[name_m]Nathan[/name_m] [name_m]Rafferty[/name_m]
[name_m]Nathan[/name_m] [name_m]Barnaby[/name_m]
[name_m]Nathan[/name_m] [name_m]Samuel[/name_m] (if you dont mind another S initial)
[name_m]Nathan[/name_m] [name_m]Gabriel[/name_m]
[name_m]Nathan[/name_m] [name_m]Frederick[/name_m]
[name_m]Nathan[/name_m] [name_m]Alistair[/name_m] / [name_m]Alasdair[/name_m] (except that you already have [name_m]Alexander[/name_m])
[name_m]Nathan[/name_m] [name_u]Rory[/name_u]
[name_m]Nathan[/name_m] [name_m]Philip[/name_m]
I love [name_m]Nathan[/name_m] [name_m]Rafferty[/name_m] and [name_m]Nathan[/name_m] [name_m]Samuel[/name_m]!
I really like the combo [name_m]Nathan[/name_m] [name_m]Gregory[/name_m]. I find it very handsome. the runners ups were [name_m]Christopher[/name_m] and [name_m]Geoffrey[/name_m], but I prefer [name_m]Gregory[/name_m].
[name_m]Nathan[/name_m] [name_m]Christopher[/name_m] flows the best although I like the suggestion of [name_m]Nathan[/name_m] [name_m]Charles[/name_m].