Nitelife Promotions offers Open Carry T-shirts that look real. While they were created by a Pro-2A business owner Paul Liebe to promote firearms, even he admits that they could be mistaken by law enforcement for a real gun. In fact, he includes this warning in his site as well as with each shirt.
They are available in a variety of sizes, colors and styles but regardless, they look real enough that it could cause some tension. I’d say that if you’re going to wear it under a vest or jacket like this photo suggests, you might as well expect some unwanted attention.
I don’t doubt the man’s dedication, I’m just questioning the execution. I’ll file this one in the “even though you could, you shouldn’t have” folder.