Aside from the suggestions that’ve already been made, #1 for me would be the Musically Yours paid field
https://forum.enlightenedstates.com/t/musically-yours/60178
It is a brain field, so it targets those aspects.
The other would be the Vocal Strengthening and Range Increaser field. It used to have a ton of amazing reviews before it got taken down (and re-uploaded)