100 mm front hub, 94 mm fork dropouts, options?
Sorry to provide ANOTHER answer, but I think this one might be interesting:


Take a rear (135mm) axle;
Insert two nuts, one around each side, untill they are less than 80mm apart. One of them might be inserted just enough to allow a small piece of thread to show up in the tip;
Fit the axle into the fork dropouts with the bike upside down, so that both nuts are beween the dropouts;
Start to "unscrew" one of the nuts, thus forcing the fork legs to get away from each other;
Unscrew it after a while and check the distance. It might take some time to figure out how much elastic deformation (preload distance) you'll have to overcome before actually making the new distance permanent.


This method is much more controlled than the lever one detailed previously, but it most probably will take much more time (although I think a rear axle and some nuts are easier to prepare than a large improvised lever system).

Hope this helps