Sabatino asked if I'd make some GUI sound effects, so I did! Download the package with 17 sounds for GUIs (click/rollover/switch) below.
It's free to use in your personal and commercial games, so don't worry about that.
Also, I'm creating Super Mario Star Scramble 3 right now, leave a comment if you've got suggestions or ideas. And yes, it'll have small Mario/big Mario/fire Mario atleast.