Dehtklok shirt I found on Redbubble by Minion-Factory thinking it had pretty cool artwork. Unsure if it's from a random artist or from an officially ran account, but the adult swim logo was in the description(something normal members on redbubble can't do) which made it look official.
Chose the classic t-shirt option because it gives it that rough textured and heavy cotton feel, like a nice quality band shirt would.