Game board battlemat
If you don't want to make your own game board, you can just buy one. The most common are the battlemats made from vinyl. When you use water-soluble markers like the Staedtler Lumocolor you can use those battlemats over and over again, since the ink is easily removed with water. Just draw the outline of your battlefield, the urban areas and the forests on the battlemat and you can start playing.
The Chessex Battlemats are widely available, but you can just search the internet for 'vinyl battlemat'. If you buy one, make sure it has a hex grid. (There are also double sided mats with squares and hexes)