You could also check REI, or a touring-oriented bike shop if there's one in the area. I was surprised to find that my local REI store stocks the Adventure Cycling maps that are relevant to our area in a hidden corner of the bicycle section of the shop. I know they have the complete Pacific Coast map series and at least the start of the Western Express, maybe others. There's also a local bike shop that specializes in touring; they have map and guidebooks in addition to racks, panniers, camping gear, and other stuff necessary for touring.