[name]Beau[/name] and [name]Cora[/name] are great together! And [name]Sylvie[/name] would be a great fit too but there are plenty of other options!
Are you explicitly avoiding matching endings to [name]Cora[/name]? I can understand that but I don’t think you have to. And do you specifically want a 1 or 2 syllable name like [name]Beau[/name] and [name]Cora[/name] or are you open to longer names? I think longer names could work.
Here are some of the first nice ones that come to mind:
[name]Beau[/name], [name]Cora[/name], and [name]Adele[/name] (French like [name]Sylvie[/name])
[name]Beau[/name], [name]Cora[/name], and [name]Alice[/name]
[name]Beau[/name], [name]Cora[/name], and [name]Amelie[/name] (some overlap with [name]Sylvie[/name])
[name]Beau[/name], [name]Cora[/name], and [name]Audrey[/name] (notes of [name]Sylvie[/name])
[name]Beau[/name], [name]Cora[/name], and [name]Cecily[/name] (some overlap between [name]Cecily[/name] and [name]Sylvie[/name], and I think you can use two C’s esp. w/ two different sounds)
[name]Beau[/name], [name]Cora[/name], and [name]Elodie[/name] (notes of [name]Sylvie[/name])
[name]Beau[/name], [name]Cora[/name], and [name]Eve[/name] ([name]Eve[/name] is faintly reminiscent of [name]Sylvie[/name], and more so with nn [name]Evie[/name])
[name]Beau[/name], [name]Cora[/name], and [name]Iris[/name]
[name]Beau[/name], [name]Cora[/name], and [name]Ivy[/name] (this one has a lot of sound overlap with [name]Sylvie[/name]!)
[name]Beau[/name], [name]Cora[/name], and [name]Jane[/name] (nn [name]Janie[/name] is cute and captures a smidge of [name]Sylvie[/name])
[name]Beau[/name], [name]Cora[/name], and [name]Lucille[/name] (French like [name]Sylvie[/name])
[name]Beau[/name], [name]Cora[/name], and [name]Lucy[/name]
[name]Beau[/name], [name]Cora[/name], and [name]Marie[/name] (notes of [name]Sylvie[/name])
[name]Beau[/name], [name]Cora[/name], and [name]Mary[/name]
[name]Beau[/name], [name]Cora[/name], and [name]Olive[/name]
[name]Beau[/name], [name]Cora[/name], and [name]Rose[/name] ([name]Rosie[/name])
[name]Beau[/name], [name]Cora[/name], and [name]Selene[/name] (some overlap)
[name]Beau[/name], [name]Cora[/name], and [name]Sophie[/name] (definitely evokes)
[name]Beau[/name], [name]Cora[/name], and [name]Willa[/name]
[name]Beau[/name], [name]Cora[/name], and [name]Zoe[/name] (some overlap)