The University of Nebraska-Lincoln Department of Mathematics has shirts for sale through Feb. 3, with two options available. The graphic shows the state outline, filled with a tiling by Sir Roger Penrose, modeled after the wooden wall piece in Avery Hall constructed by Earl Kramer, artist and emeritus professor of mathematics.
Shirts will be shipped to you directly. Order at: https://pogo.undergroundshirts.com/collections/unl-mathematics-2023-online-apparel-pop-up-shop
Once the online order form closes on Feb. 3, then all orders will be processed. Orders will ship out on Feb. 17. The form will not be reopened so you must order on or before Feb. 3 at midnight EST.
https://math.unl.edu/mathshirts