I did the same as the fellow who laminated the mat that came with the D&D adventure game, and that is a nice and easy way to do it, but I also have explored another little do-it-yourself option. In many stores, even wal-marts and k-marts, you can find Ghostline posterboard, it has very faint light grey lines marking off a lot of half-inch squares. if you are willing to take the time and trouble, you can get a good black marker and darken half the lines to make good one-inch squares, then laminate it. Also, if you want a good permanent grid of a site you will use often, but have to make yourself, you might want to use the ghostline for that, too. It comes in standard posterboard size, and a smaller size that looks about a quarter the size of regular posterboard. you also could use this to make the offset one-inch squares that some people like for having kind of a compromise between square and hex paper, but that would be considerably more work to make.
