I agree on the bit of hacksaw blade or a jigsaw blade, because the little bit of saw blade can also be useful.

One point to remember about a Ferrocerium rod is that it is the material that is removed from the rod that produces the spark.

Using real flint and steel, the flint shaves a bit of the steel and it is the sliver of steel that burns. So the type of steel is very important.

With a ferrocerium rod, it is the material shaved from the rod that burns. If you lose your scraper, you can get a good spark from a ferrocerium rod with a broken peice of glass or a sharp rock (like a flint blade). As long as it is hard and has an edge, the material used for the scraper is not that critical.