I'd buy one if my money wasn't going towards PURCHASING a Vietnamese opium den. But when I get John Smith's money (no doubt stolen, but what the hell it's an opium den) I will totally be up for getting one.
I kind of think welding goggles would be fun to sell as well. Special Doktor Sleepless ones.
I'd buy one, but don't make them too expensive, I have a list of webcomic t-shirts I desire but when you add shipping to england they end up being £20+
Also a t-shirt design competition would be brilliant. I look up http://compete-tee-tion.blogspot.com/ most days for interesting stuff and competitions to enter..
And you know you want a black armband with a white cog on it for your legion of steampunk zombie slaves to wear as they stalk through Shoreditch