Tire glue
ZAP works well so does any super glue from your local $1 store. Just use some 400grit sandpaper and scuff the bead on the rim and clean both the rim and tire with acetone or other cleaner that wont leave a film when dry anywhere where glue is to be placed. I have not had any tires come off since doing it this way. Also use tire bands, rubber bands or eletrical tape to hold the tire to the rim with pressure while drying and run a bead of glue arround edge to help seal it from dirt and rolling over.