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:

http://shop.cafepress.com/idpa?go=Go