How do I swap the retaining clip on the power button?

I bought a custom colored housing for my phone, but the power button it came with didn't have the retaining clip. I was able to remove the one from the old hardware, but now I can't get the $*#!! thing on the new power button. Short of deforming it with a pair of pliers and then trying to reshape it on the button, is there an easy way to do this??