Go to any live music show where you know people smoke. Ask anyone you see smoking if they have any to sell. You'll get turned down quite a bit, but once someone says yes, mention you are looking for a steady connection. Eventually you'll get the hang of it.

Hell, if you work in a courthouse, hang out in courtrooms and try talking to people who are there for dealing offenses. Just be warned: if they are in the courthouse already on drug charges, they probably aren't very good at it. But hey, if it's a resource you can easily exploit, why not.