I e-mailed CafePress, the company that creates the shirts, to request an exchange and had resigned myself to eating the shipping costs. And then I received this reply from a CafePress.com Support Associate:
I am sorry the item you received does not fit perfectly. I want you to be 100% satisfied with everything you purchase at CafePress.com. I am ordering you a replacement right away in the new size at no additional cost.So I have two shirts for the price of one, despite the fact that it was completely my fault ordering the incorrect size. The cherry on top: CafePress fufills SU2C orders at a 25% discount, enabling SU2C to direct the difference toward cancer research.
There is no need for a return! I do not want you to incur any additional shipping charges. Please keep the original as our way of saying thanks for shopping at CafePress.com.
I am so impressed with CafePress, and the work of SU2C, that I couldn't resist sharing my story with you. I don't get any kickbacks, pinkie promise. But please do at least consider these two organizations the next time you're feeling charitable or creative.