I don't have a Snorlax so i can't breed is their any other way of getting a Munchlax in Pokemon B/W
During the season of Summer, you can trade a Cincinno* with a person in one of the houses in Undella Bay with a Munchlax holding Leftovers.
lt is an in-game trade, and you get free Leftovers! Hooray! :D
*Thank you MeW2011!
Trade Cincino and you will get a level 60 munchlax with leftovers that knows rollout yay!