I think it is a bit excessive to carry a full repair manual around at all times, though I know many people who do.
I do think that having a wiring diagram handy is a good idea and they take up virtually no room at all. They are invaluable for the emergency "roadside tech session".
I like to enlarge one to a size that is easy to read, and then have it laminated at the local office supply or copy store. No reason to have more than one, just make sure you have the one applicable to your model year. If you have made any changes, mark them on the diagram before laminating. Don't forget to also copy that page that has the color codes and component codes, if they are not directly on the diagram. Many later manuals have one page of codes for the entire section on diagrams.
With a bit of cut and paste, you can usually put all of the pertinent information on a second sheet of paper and simply laminate it to the back of the diagram. If that does not appeal to you, do your best to note the information in fine-tipped pen on the front of your stock diagram.
You can find diagrams in the back of your manual, download them from the web, or even buy them pre-laminated.