interaction design - Need to display multi-select menu component with limited space

I am looking for a solution to display a multi-select option. Currently, we have a drop-down menu, but that is not very intuitive if user has to make multiple selections.

Any suggestions on how to convert this drop-down to a mechanism that supports multi selections, while taking into consideration space limitations. The menu bars I am looking to change are "Filter by Department" and "Filter by Discipline".