The shirts are available in Men, Women, and Youth sizes. Multiple color and style options available for each design.
For the largest number of options, styles, sizes and colors, TeeSpring. They ship domestic and internationally.
In the U.S. and in a hurry you can use Amazon.
These are the first three shirts I bought. I do love the lighter feel of direct to garment process. The top grey shirt in this picture is pretty subtle in real life. I ran all of these through a hot wash cycle with a full load of towels. Torture tested and picky ex-screen printer approved!