Same thing as before, but you have to copy the info into the mongodump command. You have to run the following commands rediculously fast, and it requires hand/eye coordination. Be warned! This is a rediculously hacky! But fun! Think of it as a video game! :D
# get the MONGO_URL string for your app
meteor mongo --url $METEOR_APP_URL
# then quickly copy all the info into the following command
mongodump -u username -p password --port 27017 --db meteor_app_url_com --host production-db-b1.meteor.io