They're hard to find, man. I used to have a shirt of 2003 Donatello that I really loved, but unfortunately, I lost it, though I've no clue how. I do recall finding a Michelangelo shirt drawn by Peter Laird, but that was in kids' sizes. Of course, I just got my brother an XL, and it fits him fine. It's such a shame that there are pretty much no TMNT shirts with original art. They're all cut and pasted from their respective show, flick, or advertisement. It's upsetting, but the best way to look is to tirelessly search various related keywords. I'm afraid I can't be of much more help than that.