What I've done before is to bring the detailed digital maps that I have into photoshop and chop them up so that I am only printing out my route with say 10km to either side. I also enlarged detailed areas, and shrunk areas with no detail. It's a lot of work, but you end up with maps customized for your route that fit perfectly into whatever you're using to protect your maps. I can usually fit a days ride on a small 8" x 6" map.

If I get disastrously off track, I buy a map from a gas station.