I'd recommend using Network Atlas to build that map. If you're monitoring all devices with Orion NPM, Network Atlas will automatically have them in it. Just build a new map and drag & drop your devices into it. It won't matter that they're not L3 connected.
Then draw in the connections and you'll be set.
Remember that when you export the map to share with others, you must share out both the html AND the .jpeg, and they both must be stored in the same folder for the html to work properly.