I'm repairing a Parker Jack Knife Safety. This Jack Knife differs from the Duofolds I've fixed in the past in that it has (or had) a single-piece button plus pressure bar. The spring part of the bar rotted completely.

What is the suggested method to repair? I've replaced pressure bars on Duofolds before, but those were a separate bar that rode in between fingers on the (separate) button. This pen has a plain button that was integral with the pressure bar/spring. Is there a replacement part available today? Or do I try to rig something together using a different pressure bar, etc.?