Hello Jerry,
Could you provide a little more information? I've never heard of "mad" brand, and searching didn't turn up anything relating to a lawn mower other than some people who were mad about some brand of mower.
To find a generic pulley, you need to know the bore size (diameter of the hole in the pulley which should be essentially the same as the diameter of the shaft the pulley is on), the diameter of the pulley (complicated; see * below), and width of the belt (or belt number). The pulley is probably keyed to the shaft, but that should be a standard size key. If it isn't keyed to the shaft, then we'll need more information about that.
*The pulley diameter is not the outside diameter of the pulley. It depends on where the belt rides in the "V" of the pulley, and more specifically, where the fibers that give the belt its strength ride on the pulley. That's usually a little under the outer surface of the belt and roughly 1/4" less than the outer pulley radius, so roughly 1/2" less than the outer pulley diameter.
You may also find this part under the name "sheave" rather than "pulley".
Do you have a part number from this "mad" company?
Give us more information and we might be able to help you find this part.