As a very long-time modeler, have you considered a rubber band motor? Very light weight, and with the proper propeller blade, they can power for a long time (>45 minutes indoors). Those are, of course, indoor models. However, outdoor versions are available with less duration. A paper outdoor model will probably not benefit from an electric motor; however, paper-balsa models will. Very small motors from pager vibrators are available. Wind speeds will have to be very low, and some skill is needed for construction.
If you really want a paper model, I suggest a balsa motor stick, paper model, and rubber band motor.