Wow! That pan is pricey these days.
I have to say that a t-shirt/jersey cake is one of the easiest to cut/create from a sheet cake. I do that most of the time because I require a shirt with more servings than the Wilton pan provides.
I run off a photo of a shirt from the internet, enlarge it, place it on the sheet cake, and cut it out. I usually wind up making a shirt body and then adding "sleeves". I torte it/them, fill, and ice.
Not exactly the way I do it, but these might help if you can't find the pan: