From the way you ask the original question this is a hypothetical, is it not? If it is then don't worry, most parts of the world will have something you can purchase so there is nothing you need to bring with you. You are not on manoeuvres, but if you are, the Army/Navy/Airforce will have something at the quartermasters. As you are enquiring about hand luggage and a messengers bag, if it does occur, just be careful.....or buy a new, cheap bag and put your old one in your checked luggage and get it repaired when you get home.