When you pull onto the main road that goes to Rosenblatt Stadium you will see stand after stand after stand selling T-shirts. The strip of road that these stands are on is about a half mile long. They are all lined up one next to the other with a few stores in between.
Most of the stands have the same shirts and the same prices. They sell shirts for each team in the tournament and as that team gets eliminated the shirts are reduced in price. They also sell several different styles of College World Series shirts. Many of the shirts are about $15-$20 depending on the shirt, team and where you get it from, and the sizes can vary from kids to adult, including women and infants. Infant sizes are more rare but you can find at least one shirt in infant sizes. If you get lucky or try you can negotiate and bargain with some of the sellers if you buy multiple shirts or something. A friend we were with got all his shirts for $10 because he bought 10 of them. I got 2 free drinks with one of my shirts and got the shirt for $5 less than another place (the shirt was for a team playing that day and in the playoffs, and it was the last one).
You will also see people selling and buying tickets to the games and trying to sell you other junk as well. You have to be aware of what is legit and what is not. Also along this road you can buy all sorts of baseball and CWS souvenirs. Everything, from bracelets, hats, socks, jerseys, bats, balls, programs, bags, etc. you name it they probably had it. You could also buy food and drinks while walking around trying to find the best deal on shirts. We picked up some ice cream (pink panthers) while walking because it was so hot and we needed to cool off.