Keep them wet until you're home.
When I first started printing my darkroom was at a friend's house, so I used to do the same thing. To get the prints home safely I acquired a large tub with a lid that seals tight. In there rest the print with little bit of water sloshing around. Too much and the prints will float around, which is a bad idea because they get creased, too little water and they dry out (depending on how long your commute is).