Some nifty USPSA oriented shirts can be found at this link:
http://shop.cafepress.com/uspsa
CafePress is a neat “make it yourself” online shirt shop. Use designs others have put up, or make your own and upload it. I’ve done it a few times before for band shirts and shirts for company parties. A bit pricey but the customizability and ability to do short runs is nice.
The IDPA section has some interesting ones too: