Is it possible to widen 96mm front fork to 100mm? It is an old Peugeot steel frame. Or should I try to find narrower lock nuts or grind them down to slimmer size?

Sheldon has good info for rear forkend but not for front fork. Maybe some good bike shop would do it for me?

Edit: uh so you do it just with bare hands? First one side and then the other one? Well I guess that could work too..