Ferrocerium Rod - Commonly known as Fire Steel, is a magnesium stick that can create spark when shave with a striker or the back of a knife. It is a preferred choice by survivalist as it is waterproof and does not use fuel. However, tinder + knowledge and skill are required if you intend to use it.
Tinder
A good knife can make fine tinder from wood or just simply use cotton balls with Vaseline for extended burning time. If your friend smoke ask them for a stick and break it, the mouthpiece contain fibrous material that can be user as tinder.
Alcohol/Surgical Spirit
Commonly use in alcohol stove. These fuel burn with blue flames and can be very difficult to spot in the day.
Hand Sanitizer
Contain alcohol, can keep your hands clean and doesn't look suspicious
Fibres
Example Lalangs and dried coconut husk
Don't wait till you need it to use it, fire steel require some practice and the best way to learn is to set campfire with it.