You could buy one or you could just download it and print it for free. All USGS maps are available for free to download. I have about 75% of California downloaded so far and am working on the rest. The link below will take you to the DRG (Digital Raster Graphics) main page. It takes some time to find what you are looking for. If the area you are looking for is in Ca. I might be
able to tell you exactly which data set to download.
Good Luck
-n
http://topomaps.usgs.gov/drg/