I sometimes use my roadbook holder as roadmap holder:
        
 
         
         
         
         
         ofcourse... you'll have to copy/cut (parts) of the original map such that they fit your roadbook.
         
        
 Mine's an ingenious one: you don't have to tape sheets together; just shove them under the foil. 
        
http://www.chalmet.net/
         
         
         
         
         This instruction video shows how it works: 
        
http://www.chalmet.net/images/handleiding.wmv
         
         HJ