recoil spring Kahr cw9

So my grandfather is getting older and losing grip strength to be able to work the action in his kahr along with his other handguns. He really likes his kahr but it has a very stiff slide to charge the gun. Does anyone know of an aftermarket recoil spring for that kahr cw9 that would help him work the slide easier?

( I know a lighter spring might affect operation of the gun but he hand-loads and is able to load rounds to help accommodate for that)