I know I'm a nobody here, but there are sites out there that would allow someone to design an official shirt and then share it with Art and whoever else for approval. Once that is done, you can receive a quote based on how many you want and the colors selected. You can even get proofs to ensure it will turn out the way you want. I ran a quick a dirty one through the system just to get something to show you. I used the graphics that were discussed above as an example. The word I have on the back "EXAMPLE" can be anything from a 501st designation or whatever else the powers that be want. I don't think this process would be impossible, I just think someone would need to bless it and someone would need to want to take it on. Food for thought .
EDIT: I could help with this endeavor if it is decided that there was a desire to move forward with it. We'd likely need to have someone like Art identify desired shirt colors as well as graphics if they are to use currently available TDH graphics. When printing though, more colors = more money, so simple may not be a horrible way to go. Based on other threads, I'll gladly let someone else take on the whole financial aspect of it, but I am offering my services to help with the design.