I’ve been thinking of making T-shirts like this for a while. Have my characters wear them, and then someone can buy a real-world version from Society6.
This one was obviously thrown together fast. You could probably make it yourself. I don’t seem to have a page on Society6 just for the basic design? Here a few of the actual shirts:
V-neck (ecru text)
Tank top (dark purple text)
Biker tank (dark purple text)
Long-sleeve (ecru text)