Illustrations of Crop Circles / Online Shop
Many different Shirts (incl. 100 % organic) in all sizes and several colours you can find in the cropcirclesindex.com T-Shirt shop at Spreadshirt. Shipping costs start at spreadshirt around 3 € in europe (incl. UK) and 9,90 € to US, Canada and some other non european countries
If you are from the USA, Canada or Australia you should also check the shop at Cafepress - there also many other products beside shirts.
Here is a preview of the available designs (barbuy casle, triple julia set, pi, the swallows and more):