Some of the downtown stations definitly have it, although I am not sure which exactly. Roosevelt should be a good bet however.

A place that I know has the passes is the CVS on the corner of State and Adams. To get there youŽd get off the orange line from MDW at Adams/Wabash and go one block west.

I agree with DavidDTW however, that MDW should have a vending machine. The passes are usually sold in smaller, orange vending machines instead of the big blue ones.