There is a map of its location on the webpage Teecee posted of the Memorial rock. It is in the southwest corner of town. Off of 5th street.
Maybe you could talk to the developer of Steward for Orbx, and see if he will add it in an update. It IS part of Stewart, after all. It should be in the scenery already, in my opinion. (although it is not really "flightsim related", come to think of it.) Just a thought.