I prefer
Isadora to
Isidora and then you can use
Sadie as a nn, even though I prefer
Isidor to
Isadore for a boy. Really dislike
Izzy. I think you can lose the second I and it still means the same thing.
I like
Jethro as well. But I know in the US it has the
Beverley Hillbillies character as a point of reference for people of my generation. In the
UK it's a more hippy
Jethro Tull kind a vibe.