Powershift was introduced in 2011, with Athena the 11-speed version. I suggest that you correctly identify what you have.
Campy has not made small parts available for it's current generation of shifters, whether Ultra-shift or Powershift.
Your choice is either to buy a complete shifter body sub-assembly, or browse the springs of the earlier generation, as some appear similar. Check out Bikeman:http://www.bikeman.com/Campagnolo_Road_Shifter_Parts.html
Excellent information! Perhaps the introduction of 11 speed shifters was Ultra Shift? I purchased mine when the 11 speed was first offered in late 2007 or early 2008.
I did look into purchasing a shifter body assembly that you have suggested, as individual parts are not sold. There are numerous sources for these kinds of sub-assemblies as it turns out. I will be ordering one in the next few days.
My LBS did something miraculous that will enable me to be on the road for the weekend. He harvested a left handed spring from a crashed lever, push one end through the inner diameter of the spring and inverted it, thereby making it a right handed spring! Installed, it shifts as good as new! We expect it to last for the next week or so until the new lever body assembly arrives.
Thanks again for your help!