There is one. Usually these are free. Road Maps can be purchased from the Visitor Information Centre, the Automobile Association shop, Bookshops and Petrol Stations. The AA Shop and big bookshops will have a good selection.
Petrol stations tend to stock regional maps only.
Visitor Information, Bookshops and the AA are likely to have the maps too. It pays to carry a light tent and be prepared to camp if travelling in the more popular places during the summer. Watch out for Giardia.