I love that shirt, too.
Wore it when I saw Superman Returns, and at my last two FoLC gatherings.
I got it through
my comic book supplier (he's awesome).
Your local comics shop might be able to help you, too. Even if they don't have it in stock, they should be able to get it. Or there are several online stores which sell them. A quick net search for "Daily Planet shirt" should turn them up easily enough. There's
this one , for example. (They have a picture of the back, too.) Or you can get it directly from
Graphitti Designs , the company that makes them (and many other cool comics-related shirts and things).