I whipped up a customisable “inventor of…” t-shirt today. The default is “robots” but really, you can claim to be the inventor of whatever you like.
The colours are customisable, too; they’re listed as “black” and “white” on Zazzle but again, that’s just the default.
Even the style is customisable. I think that covers pretty much everything you could possibly want to tinker with in a shirt without going all out and making your own.