The Lawn Stryper Lawn Striping System from S and B Lawn Systems of Waukesha, Wisconsin: Mow and Pattern Your Lawn At The SAME Time! Designed For Walk-behind Lawn Mowers! Pattern Your Lawn Like The Pros!
$80 from Hammacher Schlemmer. You attach it to your lawn mower like this:
I would imagine for some Dads would are would-be Major League groundskeepers, this would be the perfect Fathers' Day Gift.