There are some fantastic maps that you can buy from the refreshment counter at Hellasgården near Nacka, only a 15-minute bus ride from the tunnelbana station at
Slussen.
Take the #401 bus from Slussen...ask the driver if he stops at Hellasgården. Very easy and accessible. Not only are there orienteering maps at the Hellasgården refreshment stand, but also look for courses posted on the wall that you can run. And there is an old permanent course with sheet metal markers encircling tree trunks that is actually quite challenging.
Once you have the map, for future trips you can take the T-bana to Bagermossen and simply walk 500m north to the map. Swedish planning has placed a premium on retaining vast tracts of natural open space around clustered housing. Much more intelligent IMO than the US's unplanned, car-dependent suburban sprawl. Good luck! At this time of year, you should be able to enjoy many hours of fun orienteering after work.