What about Isabeau? I think it's far more plausible for a boy than Isabel. Beau is masculine, and there's also the similarity to Isadore.
♂ | Samuel ◊ Edward ◊ George ◊ Silas ◊ Arthur ◊ Ezra ◊ Freeman ◊ Dean ◊ Tobias ◊ Jasper
♀ | I'm taking a break from girls' names at the moment.