Android 4.0.4 Where to Download su or sudo Binary?
As it was correctly stated by the GiantTree, adding su binaries won't help you much as you do not have root. After rooting they more than likely will be added by default.

What concerns adding missing commands to Andorid shell, then you'd better not to do that one by one, bur rather install Busybox. It contains a big set of predefined commands.