I bought Tony Stark's orc reactor t-shirt and black sabbath t shirt from tshirtsky.com last year, so when I want the Tony Stark's shirt in Iron Man 3, my first thought is go to there to have a check. This online store didn't disappoint me again. They have listed this t shirt on their website.
Here is it:
Actually I checked some other famous online store including Amazon, Ebay, Zazzle, neither of them sells this t-shirt. Tshirtsky's Tony Stark t shirt is the mostly movie accurate one so far.
