To help you complete your mission, you need the proper equipment. The File Drawer Humidor from Altadis U.S.A. is a covert option for cigar storage in the workplace. This compact compartment will fit snuggly in your desk file drawers. The box is constructed with a dark wood exterior, and lined with Spanish cedar. The spine of the box is leather-bound so at a glance it would appear to be merely a book to the unsuspecting eye.
As for the cloud of smoke in your office and the ashes on you floor, you're on your own for now until we find some more clandestine devices. Good luck.
The File Drawer Humidor retails for $149 and is in limited supply at fine tobacconists.