If you would like to make one, you need some Iron on transfers (I used Avery brand) for dark fabric. Should be able to buy them at Best Buy. I went to Walmart and got a $3 Hanes tee, decided on dark grey with black trim around the collar and sleeves. Basically blew up the image in my sig, brightened it up a little (images tend to print out alot darker than they appear on screen). Photoshopped in the extra crap.
If you would like to make a shirt with the same image, and save some time, feel free: (make sure you print it with the page set for landscape)