From one All-Rounder owner to another, if you measure how long of a spacer you need to bridge that gap, I may be able to send you a brass M5 standoff of the correct length with M5 male and M5 female ends. Kind of like
this. BTW, because All-Rounders have semi-horizontal dropouts (at least mine does), you actually don't want to have too nice of a fender line or you may not be able to remove the rear wheel without deflating the tire.
I use standoffs with success on a few bikes to adjust the fender line (not my All-Rounder, which is currently fenderless):