The presale is over and you can now order Magic T-shirts at MTGMerch.com. There are shirts for all ten guilds, plus a shirt with the Planeswalker symbol, a shirt with the Magic logo, and a shirt with Jace.
And your feedback has been heard! There are now women's sizes! And the men's shirts go up to 3XL!
Finally, here's a quote from the FAQ that you might find interesting, especially if you're tired of things that are only available in the United States.
Do you ship internationally?
Yes, to the countries listed below. Please Note: Customers shipping to locations outside the U.S. are responsible for paying all costs associated with importing the order, including all taxes, fees and/or duties, in addition to the shipping charge. Import fees will be billed to you by FedEx, a FedEx subsidiary, or any 3rd party contractor fulfilling your shipment. The listed shipping cost covers the cost of shipping and brokerage only. All sales are final. We do not offer exchanges or refunds for international orders.
At this time, we are able to ship to the following countries: