I had someone ask me about this yesterday, so if anyone else is interested you can get a PolySkeptic T-shirts here:
BTW, I don’t get a cent from these purchases. I did the design, but I have not set up any way to get any of the proceeds.
So, if you are interested in one, there is a way to get a shirt (in various colors).
I currently have 2 of these shirts, and wear them somewhat frequently.