You never know what will happen or if you will be able to find something. So, it is good to be prepared. Tie bars are essentially one of the easiest things to find a replacement for. Paper clips of medium and large sizes works best and they can be thrown away or misplaced with no worry. As common as they are they still look simple, elegant, and interesting. Just make sure you don't get too cocky about this when you out dress the metro-guy from accounting who spent a fortune on his monogrammed, custom, white gold tie bar. By the way, you can lie to him and tell him it's sterling or really tick him off by admitting you picked up from the supply closet as you strolled in this morning.
Signed The Eccentric Orange Gentleman