Use the DataReader Source against your ODBC connection to DB2.  We use IBM's DB2 Connect software.

Under Connection Managers, right-click and select "New Connection...".

Choose ODBC.  New... Pick your ODBC connection from the drop-down list (as previously DSNs defined on your box)

From there, I then select the radio button to "Use connection string" and then on "Build".  This brings up another window.  Select the database alias, User ID, and password.  Click OK.  After it connects, test the connection.

I'm not sure this is the best way to do this, but it works for me (for now).