The NOOO honestly doesn't bother me much, but if you're changing it, I don't know if you even need a substitute for the scream at all. Just rearrange the dialogue (with a snippet or two from other Vader lines) to have his reaction to the news one of instant outrage that quickly is replaced by self-hating depression:

PALPATINE: It seems, in your anger, you killed her.

VADER: WHAT? No, I - she was alive! I...couldn't have...

Don't have him destroy the droids (CGI here always looked iffy anyway) or break off the table, either - just some subtle Force-shaking, but end either on a close-up of his face or Palpatine's.