A character in my world has the ability to greatly control flames. He can even amplify a small fire to a large inferno if necessary. However, there is one problem: He can't create fire out of nothing. He needs an already existent flame to begin using his powers. Thus, he needs some device, like a modern lighter, that provides a ready source of flames. With pre-gunpowder tech, is there any such substance or contraption?
Note: An answer need not satisfy all these conditions. However, the ones marked with an exclamation mark must be satisfied. A good answer will satisfy as many of these conditions as possible.
(!) The world is pre-Industrial, pre-gunpowder. The substance that should be used, though not necessarily be known in those times, should be able to be created using the available technology. This means, if a chemical wasn't known in the middle ages, but can be readily created using the technology available in the era, it is allowed. Note: Gunpowder is not allowed.
(!) The device should be able to be made by a group of skilled craftsmen at most, and should not require materials only readily available after Industrialisation.
The substance should be long lasting. The mage shouldn't have to go secure a supply every time he uses it to start a flame.
(!) A spark isn't enough. It should be a proper flame.
It should remain usable in as many conditions as possible, such as times of high moisture, etc.
(!) The device, that is, the substance + the mechanism to combust it, should be small enough to be carried by a person
It should be quick to combust
It should be reliable, i.e., once activated, the combusting mechanism should always make the substance combust, and it should not present harm to the mage.
Note on the abilities of the Mage
While not having access to flames, the mage can still create a small amount of heat. However, this is rather minuscule and not nearly enough to, say, boil water. It can, however, set off substances at a low ignition point.
Is there any substance that has the given properties? Or at least, as many of them as possible?