Logitech makes a great wireless. I dont currently have a picture but it pretty darn close to the standard PS2 controller.....let me see if I can find a good pic....
Ahh yes, there it is. You can walk outside and never miss a beat. I believe its 900mhz. I had a chance to use one awhile back. Its the best wireless controller on the market.
I believe it is available at Walmart for under $40.