I have used aluminum cookie sheets, fiber glass, ABS plastic, and of-course templates of cardboard and duct tape to make shrouds.

Doubt if you will find one off the shelf, however they are easy to make. Come to the middle of the blades, get as close to the od of the fan as posible (without hitting)

The problems we face today can not be addressed at the same level of intelligence we were at when we created them - Albert Einstein Or with the same level of $ - Me