if you want a proper navi system , get it from Honda center , it'll be mighty expensive the last time i checked it was for 55 k brand new , but you can get a kabuli one for half that.
Rest , go to ghawal mandi, search for a couple of days , go to each and every shop
quality varies from time to time and shop to shop , so i cant specify a shop , select the best one according to your budget , and choice
If your're new to pindi tag a Pakwheeler along , If I'am free , on a weekend i'll can send my little bro along
Regards,