My target T shirt SUCKED! It was that stressed style where the fabric is called "heather" (anyone know what I'm talking about?). I washed it 2x and by the second time I wore it the shirt was SEE THROUGH. I could see straight through it. Try to avoid that type of fabric. if anyone could better describe the fabric I'm talking about, please do. I'm probably doing an awful job of describing it lol!
If you just simply want "matching", head to the
Disney Store if your mall has one. I've heard that the Disney Store has cheaper prices than actual Disney stores on property. I am not 100% sure on this, just what I've heard. You could look online to see what the prices are on there versus in park.
If you want them customized, I think Etsy would be the cute, unique way to go. Etsy may charge a little extra because of it being handmade. The popular t shirt stores on line that do customizable stuff may be more affordable, but it's possible they only have limited designs for Disney that other people in the parks may have. If that's not a concern of yours, going that route may be your best bet.