If this goes down, the shirt needs to be well fitting. No tacky Fruit of the loom/Gildan/etc that look shaped for a block of wood.
Guessin' JoAnna (@Queen of Blades ) would have to sign off on it first. Then, maybe one could order via the store?
A cafepress type thing seems like it would be a fair option. Use the logo and maybe a couple of other designs and you can order a ton of different items. A few dollars goes to the den each sale and there really isn't any work that needs to be done since it's all handled via cafepress. At least that's how I recall it working!
Zazzle is also another option. I vaguely recall Cafepress being more expensive for product however. Both would permit you to logo more than just t-shirts. Myself - the TSD logo embroidered on a polo would be just classy...
Personally, I have been very happy with the quality of my TSD Zazzle shirt (bought a few years ago). Especially compared to any of the numerous woot shirts I've bought over the last few years.