My wife finds the standard XBOX 360 controller too large for her hands, so doesn't use the console. It seems there was a smaller controller on sale from Madcatz, but it is no longer available.
Does anyone know a good option for her?
I found the controller you were referring too (Its about 30% smaller than a regular xbox 360 controller) I couldn't find the controller on the MadCatz site, however I did find one on amazon for you.
It's important to note that xbox's stranglehold on wireless controllers actually prevents 3rd party makers from creating wireless controllers. So your wife will have to cope with the wire... Sorry.
Picture of the difference in size: