You can't find wired Xbox 360 controllers anymore because Microsoft isn't manufacturing them anymore, however you will find non-Microsoft wired controllers in the market with different brands, like Razor , a Chinese brand ect.
I have purchased a fake Microsoft wired controller in the past and I am very happy with it, my only problem is that the analogs aren't that sensitive as the genuine one and the I can't use vibration because the controller hangs, so I got no vibration and low analog sensitivity.
You can also buy a
Wireless Gaming Receiver for Windows which basically makes you run your wireless controller on your PC without any wires.